• 한국세라믹학회지
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• 제13권1호
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• pp.11-19
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• 1976

Carbon bond 흑연도가니는 clay bond 형 흑연도가니에 비하여 열전도율이 크고 열팽창율이 적으며, 열간하중성이 좋을 뿐 아니라 열충격에도 안전하여 그 사용 수명이 100여회나 된다. 본 연구결과 carbon bond 형 흑연도가니의 제조에 적합한 원료의 조합비는 인장흑연 40, 탄화규소 15, Ferro-silion 25, 무기질결합제 15, 영정석 3, ferromanganese 2 였으며, 흑연도가니 제조에 소요되는 원료들의 상호관계는 흑연량이 증가할수록 산화율 및 기공률이 증가하고, 기공률의 증가도 흑연의 산화량에 비례하였으며, 탄화규소의 증가는 산화율 및 기공률을 증가 시켰고 ferrosilion의 증가는 기공률 및 산화율에 별영향을 미치지 않었고, 유리질의 증가는 산화율 및 기공율을 감소시키나 과량이면 bloating현상이 일어나 오히려 기공률이 커졌다. 제조된 도가니의 물성은 부피비중2.31, 겉보기비중 2.58, 기공률 15.2%, 흡수율 6.01%, 압축강도 438kg/$cm^3$, 인장강도 256kg/$cm^3$, 산화소모율 3.77%이하이며 평균사용 수명은 105회였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.113-114
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• 2009

Silicon carbide is one of the most attractive and promising wide band-gap semiconductor material with excellent physical properties and huge potential for electronic applications. Up to now, the most successful method for growth of large SiC crystals with high quality is the physical vapor transport (PVT) method [1, 2]. Since further reduction of defect densities in larger crystal are needed for the true implementation of SiC devices, many researchers are focusing to improve the quality of SiC single crystal through the process modifications for SiC bulk growth or new material implementations [3, 4]. It is well known that for getting high quality SiC crystal, source materials with high purity must be used in PVT method. Among various source materials in PVT method, a SiC powder is considered to take an important role because it would influence on crystal quality of SiC crystal as well as optimum temperature of single crystal growth, the growth rate and doping characteristics. In reality, the effect of powder on SiC crystal could definitely exhibit the complicated correlation. Therefore, the present research was focused to investigate the quality difference of SiC crystal grown by conventional PVT method with using various SiC powders. As shown in Fig. 1, we used three SiC powders with different particles size. The 6H-SiC crystals were grown by conventional PVT process and the SiC seeds and the high purity SiC source materials are placed on opposite side in a sealed graphite crucible which is surrounded by graphite insulation[5, 6]. The bulk SiC crystal was grown at $2300^{\circ}C$ of the growth temperature and 50mbar of an argon pressure. The axial thermal gradient across the SiC crystal during the growth is estimated in the range of $15\sim20^{\circ}C/cm$. The chemical etch in molten KOH maintained at $450^{\circ}C$ for 10 min was used for defect observation with a polarizing microscope in Nomarski mode. Electrical properties of bulk SiC materials were measured by Hall effect using van der Pauw geometry and a UV/VIS spectrophotometer. Fig. 2 shows optical photographs of SiC crystal ingot grown by PVT method and Table 1 shows electrical properties of SiC crystals. The electrical properties as well as crystal quality of SiC crystals were systematically investigated.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.299-302
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• 2003

The interface heat transfer coefficient was measured for non-isothermal bulk forming of Ti-6Al-4V. FE analysis and experiments were conducted. Equipment consisting of AISI H13 die was instrumented with thermocouples located at sub-surface of the bottom die. Die temperature changes were investigated in related to the process variables such as reduction, lubricant and initial die temperature. The calibration approach based on heat conduction and FE analysis using an inverse algorithm were used to evaluate the interface heat transfer between graphite-lubricated die and glass-coated workpiece. The coefficients determined determined were affected mainly by the contact pressure. The validation of the coefficients was made by the comparison between experimental data and FE analysis results.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2004년도 Proceedings of the 4th Korea-China Joint Workshop on Nuclear Waste Management
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• pp.257-259
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• 2004

In this paper measurement method of uranium isotope ratio of uranium-bearing particles in swipe samples was introduced; Swipe sample screening program was proposed on the basis of studying various destructive assay and non-destructive assays. Scanning electron microscope(SEM) equipped with an energy dispersive X-ray fluorescence(XRF) system was applied to locate the deposited uranium-containing particles on the graphite support, particle's composition and size can be identified. Some isotope ratio results were compared with those of other bulk analytical methods; By measuring the same prepared sample, we got the U-particle isotopic ratio data similar to those from IAEA NWAL, indicating that our operation parameters and experimental conditions are viable and can be used for measurement of U-particle isotopic ratio from swipe samples.

• 한국세라믹학회지
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• 제28권11호
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• pp.908-916
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• 1991

The characteristics of the carbonized and calcined products made from coal tar pitch coke and coal tar pitch, were investigated in the aspect of the manufacture of isotropic graphite with high density. The mesophase from the pitch was rapidly formed at higher heat-treatment temperature between 410$^{\circ}C$ and 450$^{\circ}C$, where the insolubes in the pitch accelerated the rate of nucleation and growth of the mesophase. The benzene insolubles and the quinoline insolubes were increased as the heat treatment temperature and the heat-treatment time increased. The ratio of benzene insolubles and quinoline solubles (BI/QS) was decreased as the heat-treatment temperature was higher and maintained to be nearly constant regardless of heat-treatment time at fixed heat treatment temperature. The bulk density of the calcined carbon was linearly proportional to the ratio of quinoline solubes to volatile matter in the green coke. Anisotropic ratio of electrical resistance was measured to be between 0.98 and 1.10.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.217-217
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• 2009

In this work, the oxidation-induced characteristics of five nuclear graphites (NBG-17, NBG-18, NBG-25, IG-110, and IG-430) were studied. The oxidation characteristics of nuclear graphites were measured at the three temperature areas (300, 600, and $900^{\circ}C$). As experimental results, the pore size of oxidized graphite was increased with increasing of oxidation time. It was also found that the oxdation rate was propotional to the oxidation temperature and time. This was probably due to the oxidation was occurred on the surface and inner bulk phase of nuclear graphites at the same time by the socalled chemical regime.

• 소성∙가공
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• 제12권4호
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• pp.370-375
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• 2003

Determination of the interface heat transfer coefficient was investigated in non-isothermal bulk forming of glass-coated Ti-6Al-4V. FE analysis and experiments were conducted. Equipment consisting of AISI Hl3 die was instrumented with thermocouples located at sub-surface of the bottom die. Die temperature changes were investigated in related to the process variables such as reduction, lubricant and initial die temperature. The calibration approach based on heat conduction and FE analysis using an inverse algorithm were used to evaluate the interface heat transfer between graphite-lubricated die and glass-coated workpiece. The coefficients determined were affected mainly by the contact pressure. The validation of the coefficients was made by the comparison between experimental data and FE analysis results.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 15TH KACG TECHNICAL MEETING-PACIFIC RIM 3 SATELLITE SYMPOSIUM SESSION 4, HOTEL HYUNDAI, KYONGJU, SEPTEMBER 20-23, 1998
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• pp.35-40
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• 1998

There have two kinds of defects, planar defects and vertical defects which were called micropipes in SiC bulk crystals grown by a sublimation method. We could decrease these defects by adding a little piece of Si in the SiC powder or using Ta cylinder in the crucible. so were report the dependence of these defects in a wafer on silicon/carbon ratio in this paper. The chemical species sublimed from SiC powder is affected by carbon from the graphite wall of the crucible. It is important to control the chemical species on the substrate.

• 한국재료학회지
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• 제14권2호
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• pp.83-89
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• 2004

SiC nanotubes were synthesized by SLS growth mechanism using various metal catalysts. Synthesized nanotubes had mean diameters of 20~50 nm and several $\mu\textrm{m}$ length. The kind of catalysts affected microstructures of SiC nanotubes by different diffusion routes. These differences are attributed to catalysts' physical properties and relative activities to the graphite substrate. Fe acted as a good catalyst of SLS growth mechanism. But in case of Ni, SiC nanotubes grew slowly. Optical property was measured by photoluminescence measurement. Relatively broad peak was obtained and mean peak positioned at about 430 nm. This result was the same as other nanocrystalline SiC materials, but was different from the results of bulk SiC probably due to quantum confinement effect and defect in the grown SiC nanotube.

• Transactions on Electrical and Electronic Materials
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• 제5권5호
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• pp.204-207
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• 2004

In this work, we present the electrochemical properties of Al bipolar plate, which can be re-searched for the application of PEMFC system. Bulk resistance of the plate was measured with a four-point probe method. The electrical conductivity of noble metal coated Al plate was 4.40 x 10$^4$ S/cm. On the other hand, the electrical interfacial resistance of the noble metal coated Al plate valued at 0.15 mΩ-$\textrm{cm}^2$ and that of graphite was 0.26 mΩ-$\textrm{cm}^2$ under the holding pressure of 140 N/$\textrm{cm}^2$ at the applied current of 5 A. And the performance of Al bipolar plate for PEMFC was evaluated at various conditions. The single cell performance was more than 0.43 W/$\textrm{cm}^2$ (0.47 Wig) for noble metal coated Al bipolar plate at 5$0^{\circ}C$ under atmospheric pressure in external humidified hydrogen and oxygen condition. As the present results, we could show the results that the noble metal coated Al bipolar plates were favorable in the aspect of electrical properties compared with those of the commercialized resin-impregnated graphite plates.