• Journal of Magnetics
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• 제17권1호
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• pp.9-12
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• 2012

Attempts to dope carbon nanotube (CNT) with impurities in order to control the electronic properties of the CNT is a natural course of action. Boron is known to improve both the structural and electronic properties. In this report, we study the field emission properties of Boron-doped double-walled CNT (DWCNT). Boron-doped DWCNT films were fabricated by catalytic decomposition of tetrahydrofuran and triisopropyl borate over a Fe-Mo/MgO catalyst at $900^{\circ}C$. We measured the field emission current by varying the doping amount of Boron from 0.8 to 1.8 wt%. As the amount of doped boron in the DWCNT increases, the turn-on-field of the DWCNT decreases drastically from 6 V/${\mu}m$ to 2 V/${\mu}m$. The current density of undoped CNT is 0.6 mA/$cm^2$ at 9 V, but a doped-DWCNT sample with 1.8 wt% achieved the same current density only at only 3.8 V. This shows that boron doped DWCNTs are potentially useful in low voltage operative field emitting device such as large area flat panel displays.

• Bulletin of the Korean Chemical Society
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• 제26권8호
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• pp.1214-1218
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• 2005

Ti-HMS samples in which titanium species exist in various forms of isolated tetrahedral state, finely dispersed $TiO_2$ cluster, and some in extra-framework anatase phase were prepared via a direct synthesis route using dodecylamine (DDS) as a structure directing agent by systematically varying the titanium loadings between 2 and 50 mol% Ti/(Ti+Si) in substrate composition. Physicochemical properties of the materials were evaluated using XRD, SEM/TEM, N2 adsorption, UV-vis and XANES spectroscopies. Catalytic properties of Ti-HMS in cyclohexene and 2,6-di-tert-butyl phenol (2,6-DTBP) oxidation using aqueous $H_2O_2$, and vapor phase photocatalytic degradation of acetaldehyde were evaluated. High $H_2O_2$ selectivity was obtained in cyclohexene oxidation, and cyclohexene conversion was found primarily dependent on the amount of tetrahedrally coordinated Ti sites. For bulky 2,6-DTBP oxidation and photocatalytic oxidation of acetaldehyde, on the other hand, conversions were found dependent on the total amount of Ti sites and maintaining an uniform mesoporous structure in the catalysts was not critical for efficient catalysis.

• 청정기술
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• 제19권1호
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• pp.65-72
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• 2013

본 연구에서는 중형 기공성 실리카 담체인 MCM-41과 SBA-15를 활용하여 팔라듐과 구리를 담지한 후, 제조 촉매의 수중 질산성 질소 저감 반응 활성을 평가하였다. 순수 수소 공급 반응 조건에서, 질산성 질소의 농도는 반응 시간에 따라 점차 저감되었지만, 반응기 내부에 높게 형성된 pH로 인해 질소의 선택도가 매우 낮은 문제점이 발견되었다. 이를 해결하기 위해 이산화탄소를 수소와 함께 공급하여 pH의 안정화를 도모하였고, 질소 선택도를 40% 가량 증가시켰다. 상기 두 반응 조건에서 모두 Pd-Cu/MCM-41가 Pd-Cu/SBA-15보다 높은 활성을 나타냈다. 이와 같이 수중 질산성 질소 저감 반응의 활성에 차이를 보이는 두 촉매에 대하여, 질소 흡-탈착, XRD, $H_2$-TPR, XPS 등과 같은 특성 분석을 수행하여 제조 촉매의 구조와 물성이 반응활성에 미치는 영향을 검토해보았다.

• 한국재료학회지
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• 제26권8호
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• pp.401-405
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• 2016

The cobalt silicides were investigated for employment as a catalytic layer for a DSSC. Using an E-gun evaporation process, we prepared a sample of 100 nm-thick cobalt on a p-type Si (100) wafer. To form cobalt silicides, the samples were annealed at temperatures of $300^{\circ}C$, $500^{\circ}C$, and $700^{\circ}C$ for 30 minutes in a vacuum. Four-point probe, XRD, FE-SEM, and CV analyses were used to determine the sheet resistance, phase, microstructure, and catalytic activity of the cobalt silicides. To confirm the corrosion stability, we also checked the microstructure change of the cobalt silicides after dipping into iodide electrolyte. Through the sheet resistance and XRD results, we determined that $Co_2Si$, CoSi, and $CoSi_2$ were formed successfully by annealing at $300^{\circ}C$, $500^{\circ}C$, and $700^{\circ}C$, respectively. The microstructure analysis results showed that all the cobalt silicides were formed uniformly, and CoSi and $CoSi_2$ layers were very stable even after dipping in the iodide electrolyte. The CV result showed that CoSi and $CoSi_2$ exhibit catalytic activities 67 % and 54 % that of Pt. Our results for $Co_2Si$, CoSi, and $CoSi_2$ revealed that CoSi and $CoSi_2$ could be employed as catalyst for a DSSC.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.142.2-142.2
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• 2013

The effect of substrate on catalytic activity of CO oxidation with transition metal Platinum nanoparticles on doped and undoped TiO2 was investigated. Titanium dioxide was doped chemically with non-metal anions including nitrogen and fluorine. Undoped TiO2 was synthesized via simple conventional sol-gel route. Thin films of titania were developed by spin coating technique and the characterization techniques SEM, XRD, UV-Vis Absorption Spectroscopy and XPS were carried out to examine the morphology of films, crystal phase, crystallites, optical properties and elemental composition respectively. XPS analysis from doped TiO2 confirmed that the nitrogen site were interstitial whereas fluorine was doped into TiO2 lattice substitutionally. Catalytic activity systems of Pt/doped-TiO2 and Pt/undoped-TiO2 were fabricated to reveal the strong metal-support interaction effect during catalytic activity of CO oxidation reactions. By arc plasma deposition technique, platinum nanoparticles with mean size of 2.7 nm were deposited on the thin films of doped and undoped titanium dioxide. The CO oxidation was performed with 40 Torr CO and 100 Torr O2 with 620 Torr He carrier gas. Turn over frequency was observed two to three folds enhancement in case of Pt/doped TiO2 as compared to Pt/TiO2. The electronic excitation and the oxygen vacancies that were formed with the doping process were the plausible reasons for the enhancement of catalytic activity.

• 청정기술
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• 제16권4호
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• pp.265-271
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• 2010

경유차 매연저감장치에서 비활성화된 디젤산화촉매(DOC)를 대상으로 여러 가지 조건에서 재제조한 후, 재제조된 DOC의 일산화탄소(CO)와 탄화수소화합물(THC)의 저감효율과 촉매물성 특성을 분석하여 비활성화된 DOC 촉매에 대한 재제조 효과를 관찰하였다. 재제조된 DOC촉매에 대한 오염물질 저감성능 평가는 디젤엔진 다이나모 장치를 이용, 배기가스를 일부 우회시켜 온도와 공간속도조절이 가능한 촉매반응장치로 수행하였으며, 촉매물성 분석은 광학현미경, EDX, ICP, TGA 그리고 porosimeter를 이용하였다. 연구수행 결과 비활성화된 DOC 촉매를 본 연구에서 적용된 고온배소세정, 산성/염기성용액에 의한 초음파세정, 세정 후 촉매활성성분 재함침에 의한 재제조를 수행할 경우, 재제조된 DOC 촉매의 성능이 신품 성능의 90% 이상으로 회복되는 것을 확인하였으며, 광학현미경, EDX, TGA와 ICP등의 분석을 통해 본 연구조건에서의 재제조 과정으로, 촉매의 활성 저하 원인이 되었던 각종 불순 성분 대부분이 비활성화된 DOC 촉매로부터 제거되는 것을 확인하였다.

• 한국결정성장학회지
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• 제27권1호
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• pp.1-8
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• 2017

Metal organic chemical vapor deposition(MOCVD) 방법을 이용하여 금속 촉매에 따른 ${\beta}-Ga_2O_3$ 나노 와이어의 제작과 특성에 대해 연구하였다. 본 연구의 성장 조건에서 ${\beta}-Ga_2O_3$ 나노 와이어의 성장이 가능한 금속 촉매는 Au, Cu 그리고 Ni이 있었으며 각 금속 촉매로 성장한 나노 와이어는 성장률과 형상에 많은 차이가 있었다. Ni 촉매 성장의 경우에는 Vapor-Solid(VS) 과정이 ${\beta}-Ga_2O_3$ 나노 와이어 성장의 주된 메커니즘이고 Au, Cu 촉매 성장의 경우에는 Vapor-Liquid-Solid(VLS) 과정이 주된 성장 메커니즘 임을 확인할 수 있었다. 또한, 촉매의 종류에 따라서 ${\beta}-Ga_2O_3$ 나노 와이어의 광학적 특성도 다르게 나타나는 것을 확인할 수 있었다. 반면, 동일한 성장 조건에서 Ti, Ag 그리고 Sn 금속은 나노 와이어 성장을 위한 촉매로 작용하지 못하였다. 본 연구에서는 금속 촉매에 따른 나노 와이어의 성장 가능 여부와 성장한 나노 와이어의 특성 변화가 금속 촉매의 녹는 점, 금속- Ga의 공융 점과 관련이 있음을 상태도와 연관 지어 밝혀내었다.

• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.2961-2965
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• 2012

Mesoporous carbons with tailored pore size were prepared by using sucrose as the carbon source and silicas as the templates. The silica templates were obtained from a hydroxypropyl-${\beta}$-cyclodextrin-silica hybrids using ammonium perchlorate oxidation at different temperatures to remove the organic matter. The structures and surface chemistry properties of these carbon materials were characterized by $N_2$ adsorption, TEM, SEM and FTIR measurements. The catalytic performances of these carbon materials were investigated through the reduction of nitroaromatic using hydrazine hydrate as the reducing agent. Compared with other carbon materials, such as active carbon, and carbon materials from the silica templates obtained by using calcination to remove the organic matter, these carbon materials exhibited much higher catalytic activity, no obvious deactivation was observed after recycling the catalyst four times. Higher surface area and pore volume, and the presence of abundant surface oxygen-containing functional groups, which originate from the special preparation process of carbon material, are likely responsible for the high catalytic property of these mesoporous carbon materials.

• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2720-2724
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• 2013

Polynorbornenes prepared by vinyl addition pathway are known to have some desirable characteristics for wider application but they have some critical drawbacks such as brittleness, poor solubility and adhesion. In order to improve these drawbacks, extensive research for the successful homo- and copolymerization of polar functionalized norbornene with olefin has been carried out. Even though considerable advance has been achieved in the polymerization of polar functionalized monomers, successful catalytic systems for the homopolymerization of polar functionalized norbornene are rare. In this study, a novel successful catalytic system for the polymerization of polar functionalized norborene is proposed. This system employs Pd ${\beta}$-diketiminate/borate cocatalyst in water/organic mixed solvents and it is unique due to introduction of water as a component of solvents. Polymers obtained in this study show high Mw with narrow PDI. Effects of several reaction parameters to the polymer activity and properties are investigated and optimal catalytic system are proposed.

• KEPCO Journal on Electric Power and Energy
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• 제4권1호
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• pp.39-45
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• 2018

Ammonia Adsorbed Fly Ash (AAFA) samples produced from coal fired plants equipped with SNCR (Selective Non-Catalytic Reduction) of nitrogen oxides with urea have been chemically analyzed, and their physical and dissolution properties have been investigated. XRD results for the ammonia component in AAFA ascertained that ABS (ammonium bisulfate) and AS (ammonium sulfate) were deposited on fly ash as $SO_3$ reacted with unreacted ammonia at SNCR. SEM and EDS images showed that fine ashes on large fly ash surface of sphere type were agglomerated, due to adhesive role of ammonium salts attached fly ashes. Dissolution test results of ammonium salts absorbed on AAFA in distilled water or sea water showed that the proportion of un-ionized $NH_3$ to $NH_4{^+}$ were primarily a function of pH and temperature. Increasing pH and temperature causes an increase in the fraction of un-ionized $NH_3$. At pHs of 9.6 and 10.7, un-ionized $NH_3$ and $NH_4{^+}$ ions are present in equal amounts at distilled water and sea water, respectively.