• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.415-420
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• 1997

하나로 재료 조사시험용 표준형 계장캡슐 개발의 일환으로 캡슐 mock-up (96M-01K)을 제작하여 노외에서 승온 성능실험을 수행함으로써, 실제 하나로내 장입시의 거동 및 안전성을 평가하고자 하였다. 본 실험을 통하여 표준형 계장캡슐의 설계/제작기술, 열적조절성능, 그리고 열설계용 컴퓨터 code (GENGTC) 둥을 평가할 수 있었다. 캡슐의 진공 및 micro-heater system은 만족할만한 성능을 보였으며, 캡슐의 공기중 승은거동은 계산치와 약간의 차이는 있으나, 이는 가공/조립상의 내부 gap 변화, 캡슐표면에서의 온도측정상의 오류, 그리고 상하부로의 열손실 등에 기인하는 것으로 추정된다. 본 실험을 통하여 표준형 계장캡슐의 하나로내 건전성을 추정할 수 있었으며, 향후 하나로 장입시의 승온 및 하강절차 등을 설정할 수 있었다. 현재 본 실험 결과들을 토대로 하나로 조사시험공의 (CT, IR1, IR2) 핵적특성 평가용 표준형 계장캡슐을 (97M-01K) 설계ㆍ제작 중이다.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1994.04c
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• pp.20-20
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• 1994

• Proceedings of the Korea Water Resources Association Conference
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• 1999.05a
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• pp.131-134
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• 1999

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1997.04a
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• pp.14-14
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• 1997

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4375-4380
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• 2015

This study was performed to evaluate a newly proposed heating process of blank, which was used for Crank throw in the diesel engine, and provide design guidelines of heating processes. Non-linear numerical analyses were done using ANSYS program to investigate temperature and thermal stress distributions of blank during heating processes. The heating process consists of two stages; one is a heating stage with 20 hours, and the other is a holding stage with 12 hours, totaling 32-hour heating time. Based on analysis results, it was found that the temperature difference between the center and the surface of blank increased linearly during the heating stage but decreased gradually during the holding stage of heating processes, while max. equivalent stress, $12.5kg/mm^2$, was found at the center of blank after 10-hour heating time. As the guideline of blank heating process, it was recommended to keep the temperature difference between the center and the surface of blank to be within $150^{\circ}C$ when the environment temperature in furnace reaches $650^{\circ}C$ during a heating stage.

• Polymer(Korea)
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• v.29 no.2
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• pp.211-215
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• 2005

Stabilization process is absolutely necessary to convert the precursor fibers into chemically, physically, thermally and structurally stable carbon fibers. Especially, it is critically important for rayon fibers experiencing severe weight loss and thermal shrinkage occurring at the stabilization stage below $400^{\circ}C$. The stabilization of rayon fibers strongly depends not only on stabilization temperature but also on heating rate, chemical pre-treatment, atmosphere, and so on. In the present study, the weight loss, fiber diameter change occurred in the furnace during the stabilization process for rayon fibers produced with various heating rates and in the absence and presence of phosphorous-based flame retardants and the thermal stability of the stabilized fibers were investigated. The result indicates that the weight, diameter and thermal stability of the rayon fibers are significantly affected by the type and amount of the flame retardant used. It is also suggested that the pre-treatment of rayon fibers with a concentration lower than $3\;vol\%$ of phosphoric acid is most desirable for further carbonization process of stabilized rayon fibers.

• Fire Science and Engineering
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• v.13 no.4
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• pp.7-12
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• 1999

Thermal properties of EVA dust and its risks of coexisting with oxidizer were investigated by a pressure vessel. The decomposition of EVA dust with temperature using DSC and the weight loss with temperature using TGA were also investigated to find the thermal hazard of EVA dust. Using the pressure vessel which can estimate ignition and explosion of EVA dust coexisting with oxidizer by bursting of a rupture disc, many experiments have been conducted by varying the orifice diameter, heating rate, the weight ratio of the sample coexisting with oxidizer, and the species of oxidizer. According to the results of the thermal analysis of EVA dust, a little change of the decomposition initiation temperature with the heating rate could be found and the decomposition temperature zone of EVA dust was 250 to 50$0^{\circ}C$. The risk of EVA dust coexisting with oxidizer was increased as the orifice diameter was decreased. On the other hand, it was increased as the heating rate and the weight ratio of the sample coexisting with oxidizer were increased. In addition, the risk of EVA dust coexisting with oxidizer was affected by the decomposition temperature of the sample and oxidizer, respectively, at slow heating rate, but it was affected by the oxygen weight percent of oxidizer at fast heating rate.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.123-123
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• 2003

탄소나노튜브는 지금까지의 많은 연구를 통해 다양한 분야에 대한 응용 가능성이 확인되었으며, 그 중에서도 특히 탄소나노튜브를 이용한 전계방출표시소자(carbon nanotube field emission display, CNT-FED)는 상용화를 눈앞에 두고 있는 상황이다. 본 연구에서는 탄소나 노튜브를 합성할 수 있는 여러 가지 방법 중에서 열화학기상증착법(thermal chemical vapor deposition, thermal CVD)을 이용하여 유리기판 위에 탄소나노튜브를 합성하였다. Electron beam evaporation으로 유리기판 위에 전극층으로 Cr을 150nm를 증착하고 연속하여 촉매층인 Invar(Fe-53%Ni-6%Co 합금)를 10nm의 두께로 형성하였다. 사진식각으로 Cr층을 line 패턴한 후 Cr line 내의 Invar층을 line 및 dot 패턴하였다. 나노튜브 합성을 위해 480-58$0^{\circ}C$까지 진공분위기 또는 질소 분위기에서 20분간 승온한 후 CO(150sccm)와 H$_2$(1200sccm)를 주입하여 20분간 성장시키고 질소 분위기에서 냉각시켰다. 성장된 탄소나노튜브는 SEM, TEM, Raman spectroscopy 등을 통하여 구조 및 형상분석을 하였다. 진공승온의 경우 탄소불순물인 a-C이 많은 양 증착 되었으며 탄소나노튜브는 온도에 따라 1-5$\mu\textrm{m}$의 두께로 성장하였으나, 질소분위기 승온의 경우는 a-C이 거의 증착되지 않았으며 나노튜브의 두께가 10-20$\mu\textrm{m}$였다. 본 연구에서는 diode구조를 갖는 탄소나노튜브 에미터의 수명예측을 위해 여러 가지 가속측정조건에서 전계방출 특성을 연구하였다. Anode와 cathode 간의 간격을 400$\mu\textrm{m}$로 유지한 diode 구조에 대해 $10^{-6}$ torr 이하의 진공에서 전계방출을 측정하였다. 100 line의 에미터를 60Hz의 주파수에서 1/100 duty로 구동하였으며, duty비 증가에 따라 pulse의 on-time을 고정하고 frequency를 변화시켰다. dc까지 duty비가 증가됨에 따라 방출전류의 양이 선형적으로 증가하였다. 전압을 일정하게 고정시키고 각 duty비에서 시간에 따라 방출전류를 측정한 결과 duty비가 높을수록 방출전류가 시간에 따라 급격히 감소하였다. 각 duty비에서 방출전류의 양이 1/2로 감소하는 시점을 에미터의 수명으로 볼 때 duty비 대 에미터 수명관계를 구해 높은 duty비에서 전계방출을 시킴으로써 실제의 구동조건인 낮은 duty비에서의 수명을 단시간에 예측할 수 있었다.

• Clean Technology
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• v.22 no.1
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• pp.9-15
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• 2016

xAl-yZr mixed oxide catalysts with different molar ratios of Al/(Al+Zr) were prepared by a co-precipitation method and its catalytic performance was compared in the iso-propanol dehydration as a model reaction. The catalysts were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), N₂ adsorprion-desorption, NH₃ temperature programmed desorption (NH₃-TPD), and iso-propanol TPD analyses. The addition of Al into ZrO₂ promoted the formation of relatively small particles with large surface areas and retarded the transformation of teragonal phase to monoclnic phase. NH₃-TPD results revealed that the relative acidity of the catalysts increased along with the increase of Al molar ratio. The catalytic activity for the dehydration of iso-propanol to propylene was also increased with the same tendency. The catalytic activity could be correlated with high surface area, acidity and easy desorption of iso-propanol.

• Journal of the Korean Wood Science and Technology
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• v.38 no.3
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• pp.205-212
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• 2010

This study was carried out to investigate the characterization of aerogel made by holocellulose, the thermal properties of the aerogel, and its shapes and porous structures. The aerogel was made by holocellulose through the gelation in alkali hydroxide-urea solution and freeze drying processes. Holocellulose aerogel had porous structure such as net or sponge. The density of holocellulose aerogel was 0.04 g/$cm^3$, and the specific surface area 145.3 $m^2$/g. Although thermal degradation occurred in the range of $210{\sim}350^{\circ}C$, significant thermal degradation occurred at low temperature with low heating rate, Micropore volume was sharply increased with low heating rate. Holocellulose aerogel char obtained by carbonization with $900^{\circ}C$ and $0.5^{\circ}C$/min. heating rate had the highest surface area, 656.7 $m^2$/g. The deformed and irregular structures of holocellulose aerogel chars due to the thermal degradation were observed in SEM.