• Journal of the Korean Chemical Society
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• v.34 no.2
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• pp.136-142
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• 1990

PMO (Pertubation Molecular Orbital) energies, ${\delta}E$, have been calculated from NBMO (Nonbonding Molecular Orbital) coefficient for some hydrocarbons by PMO method. It was found that the stabilization energies are correlated with activation energies, bond dissociation energies, and G-values observed from vapor phase radiolysis in the free radical reactions.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.5
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• pp.512-522
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• 2008

Ammonia is a major compound of odor in livestock house. To enhance the performance of ammonia oxidation (decomposition). the gas-liquid, two phase photocatalytic oxidation system was designed and prepared in this study. Commercial P-25 as $TiO_2$ catalyst was used for ammonia decomposition. V/P-25 catalyst prepared by sol gel method was also used for the removal of by-producted $NO_x$ in $NH_3$ oxidation reaction. When $TiO_2$ was used as a photocatalyst, the conversion to $N_2$ in ammonia decomposition reached above 90% until 200hr (The air flow rate of 4L/min with the ammonia concentration up to 25ppm.). However, considerable amounts of NO and $NO_2$ were formed as a result of $NH_3$ oxidation (as a by-product). Therefore, we added Vanadia impregnated $TiO_2$(P-25) catalyst for the removal of $NO_x$ at the end of reaction trail. The results of a pilot-scale operation were successful to achieve the simultaneous removal of $NH_3\;and\;NO_x$ about 81 and 87%, respectively.

• Journal of Hydrogen and New Energy
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• v.12 no.3
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• pp.219-229
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• 2001

Hydrogen production by a 2-step water-splitting thermochemical cycle using metal oxides (ferrites) redox pairs and $CH_4$ have been studied in this experiment. The ferrites were reacted with $CH_4$ at $700{\sim}800^{\circ}C$ to produce CO, $H_2$ and various reduced phases (reduction step); these were then reoxidized with water vapor to generate $H_2$ in water-splitting step (oxidation step) at $600{\sim}700^{\circ}C$. The reduced ferrites, Ni-FeO and Ni-Fe alloy showed respectively different reactivity for $H_2$ formation from $H_2O$. In reduction reaction at $800^{\circ}C$, carbon was deposited on surface of Ni-ferrite due to $CH_4$ decomposition. This reduced phase containing carbon, which was taken quite different feature from other phase, produced $H_2$, CO, $CO_2$ by reacting with $H_2O$ at $600^{\circ}C$. The amount of $H_2$ evolved using reduced phase containing carbon was much higher than that of other phase.

• Polymer(Korea)
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• v.30 no.3
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• pp.210-216
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• 2006

To use the filter materials for selective removal of carbonyl compounds in cigarette mainstream smoke, hydrazine such as 2,4-dinitrophenylhydrazine (2,4-DNPH) and dansylhydrazine (DAH) impregnated adsorbents were prepared with perchloric acid or phosphoric acid as an accelerator in hydrazone formation reaction. Changes of molecular structure and morphology of adsorbents in various of impregnator were investigated by FTIR/ATR and SEM. Impregnation amount caused by reaction time, acid type and impregnation reagent, and the adsorption properties of carbonyl compounds in cigarette mainstream smoke were studied. Amounts of impregnation increased with increasing reaction time. The removal amount for vapor phase carbonyl compounds by 2,4-DNPH impregnated adsorbent was higher than that of dansylhydrazine impregnated adsorbent. The selectivity of 2,4-DNPH impregnated polyacrylic type adsorbent was superior to those of other adsorbents. This result indicates that the 2,4-DNPH impregnated polyacrylic adsorbent is applicable to cigarette filter material because of its fast reactivity and porosity.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.225-230
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• 1999

Low pressure metal organic chemical vapor deposition (LPMOCVD) of $Li_2O$ solid thin films from Li(DPM) in nitrogen-oxygen or argon-oxygen atmosphere was experimentally investigated by using a small hot wall tubular type reactor. XRD and ESCA analysis revealed that $Li_2CO_3$ film grew in nitrogen-oxygen atmosphere and $Li_2O$ grew in argon-oxygen atmosphere. The grown lithium oxide or carbonate reacted with silicon or silica base materials to produce silicates. The CVD model analysis by means of the well-known micro trench method and Monte Carlo simulation was not fully successful, but a set of data on gas phase reaction rate constant and surface reaction constant was obtained.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.10
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• pp.113-123
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• 1990

Tungsten film was deposited on the single crystal silicon wafer in a low pressure chemical vapor deposition reactor from silane and tungsten hexafluoride in the temperature range of $250-400^{\circ}C$ Deposition rate was found to be determined by the mass transfer rate of reactants from the gas phase to the safter surface. It was found out that tungsten films deposited contained about 3 atomic $\%$ of silicon and that the crystallinity and the grain size increased as the deposition temperature was increased. The resistivity of the film was measured to be in the range of $7~25{\mu}{\Omega}-cm$ and decreased with increasing deposition temperature. The adhesion of the tungsten film on a silicon surface was measured by the tape peel off test and it was improved with increasing deposition temperature. From the analysis of the gas composition, the reaction pathway to form $SiF_{4}$ and $H_{2}$ was found to be more favorable than HF formation.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.132-132
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• 2011

For the programming volume of PRAM, Ge2Sb2Te5(GST) thin films have been dominantly used and prepared by physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD). Among these methods, ALD is particularly considered as the most promising technique for the integration of PRAM because the ALD offers a superior conformality to PVD and CVD methods and a digital thickness control precisely to the atomic level since the film is deposited one atomic layer at a time. Meanwhile, although the IST has been already known as an optical data storage material, recently, it is known that the IST benefits multistate switching behavior, meaning that the IST-PRAM can be used for mutli-level coding, which is quite different and unique performance compared with the GST-PRAM. Therefore, it is necessary to investigate a possibility of the IST materials for the application of PRAM. So far there are many attempts to deposit the IST with MOCVD and PVD. However, it has not been reported that the IST can be deposited with the ALD method since the ALD reaction mechanism of metal organic precursors and the deposition parameters related with the ALD window are rarely known. Therefore, the main aim of this work is to demonstrate the ALD process for IST films with various precursors and the conformal filling of a nano size programming volume structure with the ALD?IST film for the integration. InSbTe (IST) thin films were deposited by ALD method with different precursors and deposition parameters and demonstrated conformal filling of the nano size programmable volume of cell structure for the integration of phase change random access memory (PRAM). The deposition rate and incubation time are 1.98 A/cycle and 25 cycle, respectively. The complete filling of nano size volume will be useful to fabricate the bottom contact type PRAM.

• Journal of the Korean Ceramic Society
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• v.37 no.11
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• pp.1091-1096
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• 2000

본 연구에서는 기상 반응법을 이용하여 TMS(Tetramethylsilane:Si($CH_3$)$_4$)와 NH$_3$그리고 H$_2$의 혼합기체로부터 반응 온도 1000~120$0^{\circ}C$ 및 입력비(NH$_3$/Si($CH_3$)$_4$) 1~3의 조건에서 초미분의 SiC-Si$_3$N$_4$복합 분말을 합성하였다. 합성되어진 복합 분말들의 결정상의 변화와 평균 입경을 알아보기 위해 XRD와 TEM 분석을 행한 결과, 구형의 비정질 분말이 형성되었으며, 입자의 크기는 약 70~130nm이었다. 입자의 크기는 입력비에 관계없이 거의 일정하였으나 반응 온도가 증가함에 따라서 감소하였다. FT-IR과 EA 분석 결과, 합성되어진 분말은 Si, N, C, 그리고 H로 이루어진 화합물임을 확인할 수 있었다. 또한 입력비가 다른 조건에서 합성되어진 분말을 $N_2$분위기 하에서 155$0^{\circ}C$로 2시간 열처리를 행한 결과, 낮은 입력비인 경우 $\beta$-SiC, $\alpha$-Si$_3$N$_4$와 $\beta$-Si$_3$N$_4$의 결정상들이 혼재하였으나, 높은 입력비인 경우는 결정화 후 $\alpha$-Si$_3$N$_4$상만이 존재하였다.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2830-2844
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• 2012

This review covers recent developments in our group regarding the synthesis, characterization and applications of single-crystalline one-dimensional nanostructures based on a wide range of material systems including noble metals, metal silicides and metal germanides. For the single-crystalline one-dimensional nanostructures growth, we have employed chemical vapor transport approach without using any catalysts, capping reagents, and templates because of its simplicity and wide applicability. Au, Pd, and Pt nanowires are epitaxially grown on various substrates, in which the nanowires grow from seed crystals by the correlations of the geometry and orientation of seed crystals with those of as-grown nanowires. We also present the synthesis of numerous metal silicide and germanide 1D nanostructures. By simply varying reaction conditions, furthermore, nanowires of metastable phase, such as $Fe_5Si_3$ and $Co_3Si$, and composition tuned cobalt silicides (CoSi, $Co_2Si$, $Co_3Si$) and iron germanides ($Fe_{1.3}Ge$ and $Fe_3Ge$) nanowires are synthesized. Such developments can be utilized as advanced platforms or building blocks for a wide range of applications such as plasmonics, sensings, nanoelectronics, and spintronics.

• Journal of Powder Materials
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• v.23 no.4
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• pp.297-302
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• 2016

Ag nanoparticles are extensively studied and utilized due to their excellent catalysis, antibiosis and optical properties. They can be easily synthesized by chemical reduction methods and it is possible to prepare particles of uniform size and high purity. These methods are divided into vapor methods and liquid phase reduction methods. In the present study, Ag particles are prepared and analyzed through two chemical reduction methods using solvents containing a silver nitrate precursor. When Ag ions are reduced using a reductant in the aqueous solution, it is possible to control the Ag particle size by controlling the formic acid ratio. In addition, in the Polyol process, Ag nanoparticles prepared at various temperatures and reaction time conditions have multiple twinned and anisotropic structures, and the particle size variation can be confirmed using field emissions scanning electron microscopy and by analyzing the UV-vis spectrum.