• 한국재료학회지
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• 제25권7호
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• pp.341-346
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• 2015

The feasibility of obtaining graphitic carbon films on targeted substrates without a catalyst and transfer step was explored through the pyrolysis of the botanical derivative camphor. In a horizontal quartz tube, camphor was subjected to a sequential process of evaporation and thermal decomposition; then, the decomposed product was deposited on a glass substrate. Analysis of the Raman spectra suggest that the deposited film is related to unintentionally doped graphitic carbon containing some $sp-sp^2$ linear carbon chains. The films were transparent in the visible range and electrically conductive, with a sheet resistance comparable to that of graphene. It was also demonstrated that graphitic films with similar properties can be reproduciblyobtained, while property control was readily achieved by varying the process temperature.

• Macromolecular Research
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• 제12권5호
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• pp.466-473
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• 2004

We have used FT-IR spectra to explain the effects of hydrogen bonding between chitosan and polycaprolactam (PA6). A dynamic mechanical analysis study suggested that the optimum chitosan and PA6 miscibility under the conditions of this experiment were obtained at a blending ratio of 40:60. We studied the thermal degradation of chitosan blended with PA6 (chitosan/PA6) by thermogravimetric analysis and kinetic analysis (by the Ozawa method). Dry chitosan and PA6 exhibited a single stage of thermal degradation and chitosan/PA6 blends having> 20 wt% PA6 exhibited at least two stages of degradation. In chitosan/PA6 blends, chitosan underwent the first stage of thermal degradation; the second stage proceeded at a temperature lower than that of PA6, because the decomposition product of chitosan accelerated the degradation of PA6. The activation energies of the blends were between 130 and 165 kJ/mol, which are also lower than that of PA6.

• Bulletin of the Korean Chemical Society
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• 제24권11호
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• pp.1618-1622
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• 2003

The photochemical reactions of methanolic nalidixic acid (NAL) solution in the absence and in the presence of air have been investigated using 300 nm UV light. From the reactions, 1-ethyl-7-methyl-4-oxo-4-hydro-1,8-naphthyridine (EMDN),formic acid, and formaldehyde are produced. In the presence of air, hydrogen peroxide is also detected along with the products listed above. The presence of oxygen during the irradiation of methanolic NAL solution effects on the product yield. The initial quantum yields of the products and of the NAL decomposition are determined. Possible reaction pathways for the photochemical reaction are suggested on the basis of the products analysis.

• Bulletin of the Korean Chemical Society
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• 제11권3호
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• pp.214-220
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• 1990

We have studied the Infrared Multiphoton Dissociation (IRMPD) of 1-bromo-3-chloropropane by using the pulsed $CO_2$ laser. The product yields and the HCl/HBr branching ratios in IRMPD of $BrCH_2CH_2CH_2Cl$ are studied under the focused beam geometry as a function of buffer gas (He) pressure, laser energy, and photolysing wavelength. It is observed that the total dissociation yield has a laser energy dependence of 1.8-2.0 power order and the branching ratio is very slightly dependent on the pulse energy for the laser lines employed. The dependences of total dissociation yield and branching ratio on the buffer gas pressures show that the dissociation yield monotonically decreases and the branching ratio slightly decreases with the increase of the buffer gas pressure. The Energy-Grained Master Equation (EGME) was applied to explain the laser pulse energy and the buffer gas pressure(He) dependence of the dissociation yield and the branching ratio.

• 무역학회지
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• 제46권5호
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• pp.115-130
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• 2021

The main purpose of this study is to analyze the causal relationship between import-export goods and transportation modes. To this end, five major commodity groups were selected from 2010 to 2018 such as Machinery and transport equipment (SITC 7), manufactured goods classified chiefly by material (SITC 6), chemicals and related products, n.e.s. (SITC 5), mineral, fuels, lubricants, and related materials (SITC 3), and miscellaneous manufactured articles (SITC 8). And using the panel VECM, the difference between transportation modes such as ports and airports was compared and analyzed through panel granger causality, Impulse response function, Forecasting error variance decomposition. As a result, it is confirmed that the causal relationship between major product groups and transportation modes showed different causal relationships depending on the characteristics of port and air transportation.

• 한국세라믹학회지
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• 제49권4호
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• pp.363-368
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• 2012

Nitriding and post-sintering behavior of powder mixture compacts were investigated. As mixture compacts are different from simple Si compacts, the fabrication of a sintered body with a mixture composition has engineering implications. In this research, in specimens without a pore former, the extent of nitridation increased with $Si_3N_4$ content, while the highest extent of nitridation was measured in $Si_3N_4$-free composition when a pore former was added. Large pores made from the thermal decomposition of the pore former collapsed, and they were filled with a reaction product, reaction-bonded silicon nitride (RBSN) in the $Si_3N_4$-free specimen. On the other hand, pores from the decomposed pore former were retained in the $Si_3N_4$-added specimen. Introduction of small $Si_3N_4$ particles ($d_{50}=0.3{\mu}m$) into a powder compact consisting of large silicon particles ($d_{50}=7{\mu}m$) promoted close packing in the green body compact, and resulted in a stable strut structure after decomposition of the pore former. The local packing density of the strut structure depends on silicon to $Si_3N_4$ size ratio and affected both nitriding reaction kinetics and microstructure in the post-sintered body.

• 대한기계학회논문집B
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• 제41권10호
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• pp.639-647
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• 2017

Solid SCR에 사용 가능한 암모니아 저장물질의 하나인 암모니움 카바메이트는 열 분해시 이산화탄소 가스와 암모니아 가스를 생성하며, 분해 온도인 $60^{\circ}C$ 이하에서 암모니움 염으로 재결합되는 단점이 있다. 이러한 재결합 현상을 극복하기 위하여, 희석기체인 압축공기를 이용하여 기초가시화 실험을 수행하였다. 또한, 재결합 현상을 계량화하기 위하여, 재결합 물질의 무게변화를 측정하기 위한 간단한 장치를 만들어 자동차환경에서 사용되는 SUS재질의 3가지 관경에 크기에 대한 상관관계를 검토하였다. 아크릴 튜브로 제작된 온도조절이 가능한 가시화 실험장치에, 암모니아 가스, 이산화탄소 가스, 희석기 체인 질소 가스를 공급하며, 재결합 방지를 위한 온도, 압력, 희석유량과의 관계를 고찰하고, Chapman-Enskog Theory에서 파생된 Diffusivity를 사용하여 재결합 조건을 유추할 수 있는 지표로 사용하고자 한다.

• 한국산학기술학회논문지
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• 제13권7호
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• pp.3261-3266
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• 2012

수소발생 및 저장 물질로서 붕수소화나트륨($NaBH_4$)은 촉매 분해반응을 통하여 수소를 생성할 수 있는데, 이 프로타이드 화합물을 이용하여 가정용 또는 이동용 연료전지의 수소를 공급할 수 있어서, 이 화합물과 분해반응에 대한 연구가 많이 수행되고 있다. 본 연구에서는 알칼리성 $NaBH_4$ 수용액을 귀금속이 담지된 금속산화물 촉매를 이용하여 가수분해반응을 일으키고, 그 분해반응 산물인 수소의 발생량을 측정하였다. 지지체로 사용한 금속산화물의 종류를 비교하고, 함침된 귀금속으로서 백금과 루테늄을 비교하였으며, 촉매사용량, $NaBH_4$ 용액의 농도 등의 영향을 고찰하고, 수소 발생 패턴을 조사하였다.

• 대한화학회지
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• 제27권1호
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• pp.38-45
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• 1983

아지리딘 유도체들은 저온에서 아지리딘 N-옥시드 화합물들을 생성하는데 쓰여졌으며, 이 N-옥시드 화합물들은 수소이온이 첨가된 아지리딘처럼 실온에서 쉽게 분해하거나 또는 자리 옮김 반응을 일으켰다. N-옥시드 화합물이 분해하여 생성되는 니트로소 3차 부탄 화합물은 푸른색을 띄므로 쉽게 알 수 있다. 이 화합물은 아지리딘 고리의 탄소원자에 알킬기가 치환되지 않고, 아지리딘의 질소원자에 3차 부틸기와 같이 N-옥시드 자리옮김 반응이 불가능할 경우에 주요생성물임을 밝혔다. 그러나 알킬기로 치환되었을 경우 메틸기일 때는 대부분의 아지리딘이 시그마트로픽 자리옮김 반응이 일어나 올레핀 화합물이 생성되었다. 이때 아지리딘 고리의 질소에는 3차 부틸기가 치환된 때이다. 만일 질소에 3차 부틸기를 에틸기로 치환하면 아지리딘 고리에 자리옮김 반응이 일어나지 않고 에틸기가 에틸렌으로 제거 반응이 일어나서 N-히드록시 아지리딘 화합물이 생성되었다.

• 한국세라믹학회지
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• 제28권9호
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• pp.667-674
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• 1991

In this study, Kaolin was carbonized at 1300~175$0^{\circ}C$ and its constituent mineral change was investigated. Carbonized kaolin at 1$650^{\circ}C$ was mixed with metallic silicon, formed and nitrified at 135$0^{\circ}C$ in N2-NH3 atmosphere. Properties of this product such as porosity, bulk density, MOR, nitrization rate and oxidation resistence were measured, and its mineralogical changes were investigated by XRD. The results were as follows; 1) $\beta$-SiC was initially synthesized at 150$0^{\circ}C$, and its amount was continuously increased with reaction temperature to 1$700^{\circ}C$. 2) At 1$600^{\circ}C$, mullite was rapidly decomposed and the amounts of $\beta$-SiC and $\alpha$-Al2O3 were increased simultaneously. 3) By adding alkali to kaolin, the decomposition temperature of mullite was dropped approximately 10$0^{\circ}C$, but the amount of $\alpha$-SiC was increased. 4) The highest values of their nitrization rate and MOR were obtained at the specimen of 35 wt% metallic silicon in nitrization reaction. 5) It seems that increment of $\alpha$-Si3N4 and $\alpha$-Al2O3 phase during nitrization was due to the decomposition of Al4SiC4 existed in carbonized kaolin. 6) Si3N4 bonded SiC-Al2O3 composite were fabricated from kaolin at relatively low temperature (135$0^{\circ}C$).