• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.122-122
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• 1999

Graphite with its advantages of high thermal conductivity, low thermal expansion coefficient, and low elasticity, has been widely used as a structural material for high temperature. However, graphite can easily react with oxygen at even low temperature as 40$0^{\circ}C$, resulting in CO2 formation. In order to apply the graphite to high temperature structural material, therefore, it is necessary to improve its oxidation resistive property. Silicon Carbide (SiC) is a semiconductor material for high-temperature, radiation-resistant, and high power/high frequency electronic devices due to its excellent properties. Conventional chemical vapor deposited SiC films has also been widely used as a coating materials for structural applications because of its outstanding properties such as high thermal conductivity, high microhardness, good chemical resistant for oxidation. Therefore, SiC with similar thermal expansion coefficient as graphite is recently considered to be a g행 candidate material for protective coating operating at high temperature, corrosive, and high-wear environments. Due to large lattice mismatch (~50%), however, it was very difficult to grow thick SiC layer on graphite surface. In theis study, we have deposited thick SiC thin films on graphite substrates at temperature range of 700-85$0^{\circ}C$ using single molecular precursors by both thermal MOCVD and PEMOCVD methods for oxidation protection wear and tribological coating . Two organosilicon compounds such as diethylmethylsilane (EDMS), (Et)2SiH(CH3), and hexamethyldisilane (HMDS),(CH3)Si-Si(CH3)3, were utilized as single source precursors, and hydrogen and Ar were used as a bubbler and carrier gas. Polycrystalline cubic SiC protective layers in [110] direction were successfully grown on graphite substrates at temperature as low as 80$0^{\circ}C$ from HMDS by PEMOCVD. In the case of thermal MOCVD, on the other hand, only amorphous SiC layers were obtained with either HMDS or DMS at 85$0^{\circ}C$. We compared the difference of crystal quality and physical properties of the PEMOCVD was highly effective process in improving the characteristics of the a SiC protective layers grown by thermal MOCVD and PEMOCVD method and confirmed that PEMOCVD was highly effective process in improving the characteristics of the SiC layer properties compared to those grown by thermal MOCVD. The as-grown samples were characterized in situ with OES and RGA and ex situ with XRD, XPS, and SEM. The mechanical and oxidation-resistant properties have been checked. The optimum SiC film was obtained at 85$0^{\circ}C$ and RF power of 200W. The maximum deposition rate and microhardness are 2$mu extrm{m}$/h and 4,336kg/mm2 Hv, respectively. The hardness was strongly influenced with the stoichiometry of SiC protective layers.

• Carbon letters
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• 제4권1호
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• pp.36-39
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• 2003

Carbon and carbon-based materials are used in nuclear reactors and there has recently been growing interest to develop graphite and carbon based materials for high temperature nuclear and fusion reactors. Efforts are underway to develop high density carbon materials as well as amorphous isotropic carbon for the application in thermal reactors. There has been research on coated nuclear fuel for high temperature reactor and research and development on coated fuels are now focused on fuel particles with high endurance during normal lifetime of the reactor. Since graphite as a moderator as well as structural material in high temperature reactors is one of the most favored choices, it is now felt to develop high density isotropic graphite with suitable coating for safe application of carbon based materials even in oxidizing or water vapor environment. Carboncarbon composite materials compared to conventional graphite materials are now being looked into as the promising materials for the fusion reactor due their ability to have high thermal conductivity and high thermal shock resistance. This paper deals with the application of carbon materials on various nuclear reactors related issues and addresses the current need for focused research on novel carbon materials for future new generation nuclear reactors.

• 소성∙가공
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• 제21권1호
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• pp.13-18
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• 2012

During warm forging, materials are formed in the temperature range of $300^{\circ}C\sim900^{\circ}C$. In this temperature range, the friction between the forging die and the material is very high and has a negative effect on the forming process causing severe die wear and possible defects in the component because of stick-slip. Thus, lubrication characteristics are a very important factor for productivity during warm forging. In this paper, ring compression experiments were conducted to estimate the friction factor between the die and the materials as the main factor in characterizing the lubricant. Also, ring tests using normal graphite power as a lubricant coating system were compared with tests using nano graphite powder. The results confirm that the nano graphite is superior to the normal graphite in view of its lubricating effect. In addition, the friction factor (m) was estimated with respect to the amount of the nano graphite content in the lubricant. With 10 % nano graphite the friction factor had the lowest value as compared to other amounts. It can be concluded that the amount of the nano graphite in the coating system can be optimized to obtain the best lubrication condition between the die and the material using ring test experiments.

• 설비공학논문집
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• 제16권5호
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• pp.430-437
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• 2004

This paper is intended as an investigation of study on the thermal and electrical characteristics of the carbon heating element. In this experimentation, the electric material used is the crystalline graphite a kind of natural graphite. The bentonite is used to solidify the heating element and the vacuum furnace is used for sintering it. It is noted that the natural drying time should be at least 58 hours. The plating of the electric pole with the electroless nickel showed the lowest contact resistance among others. The resistance shows linear variation with regard to length. For the insulation and resolution, the glaze coating is best with 80% of water content. The temperature rising characteristic of the heating element is better than sheath heater saving 43% of rising time. The correlation equation for temperature was obtained with the electric power.

• 한국결정학회지
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• 제8권2호
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• pp.154-159
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• 1997

0.2M TiCl4 수용액에 특수열 코팅 처리하여 TiO2 코팅된 흑연 분말 표면의 개질에 관하여 연구하였다. 35℃ 반응온도에서 TiO2 rutile상이 흑연 분말에 코팅되엇다. 코팅된 흑연 분말은 물에 대한 친수성이 증가하였다. 반응온도가 60℃로 증가함에 따라 코팅되는 TiO2의 양도 증가하였다. TiO2 코팅된 흑연 분말의 산화시작온도는 30'C 정도 증가하였고 최종감량효과도 30%이상 증가하였다.

• 한국표면공학회지
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• 제52권6호
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• pp.321-325
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• 2019

Triso-type coating layers of silicon carbide and graphite on UO₂ paticulate nuclear fuel were prepared by using fluidized bed type chemical vapor deposition and self-propagating high temperature synthesis methods to make a coated nuclear fuel of a power plant for hydrogen mass-production. The source and carrier gases were the mixture of methyltrichlorosilane and propane, and inert argon. Chemical analysis and microstructure observation showed that the coated layers were inner graphite, middle silicon carbide and outer graphite. The elastic modulus and nano-hardness of the silicon carbide layer were 503 [GPa] and 36 [GPa], respectively.

• 한국세라믹학회지
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• 제31권8호
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• pp.874-878
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• 1994

To increase the anti-oxidation and anti-wear properties of graphite for the propellant-burning environment, SiC, Pt and Al2O3 multi-layer coatings were conducted succesisvely and the optimum condition was researched. The SiC layer was produced by pack cementation and SiC layer in thickness of 30 ${\mu}{\textrm}{m}$ coating was produced after coating for 6 hours. Pt layer was coated by sputtering, and the Al2O3 layer was coated by reactive sputtering. the thickness of Pt layer and Al2O3 layer was less than one-tenth of that of SiC layer. The pack coated specimens and multi-layer coated specimens were made using above conditions and test-fired. The test result showed that the wear rate of SiC layer is approximately 1/10 compared to that of uncoated graphite.

• 한국세라믹학회지
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• 제19권1호
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• pp.44-50
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• 1982

Drawing optical fibers in a graphite furnace is one of the most convenient and economical means of producing optical fiber. Since the flaw formation on optical fiber is mainly due to dust contaminations during drawing and surface corrosion by water vapor penetration through coating layer, the tensile strength of optical fiber drawn in a graphite furnace is greatly inflenced by the drawing conditions. The important factors found in this investigation were preform treatment (fire polishing), furnace interior environment (dust contamination, inert gas flows), primary coating condition (resin curing temperature, coating materials, method, thickness) and fiber pulling condition (furnace temperature, drawing speed, pulling tension). The tensile strength at optimum drawing conditions turned out to be 5 ~ 6 GPa.

• 한국주조공학회지
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• 제5권3호
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• pp.19-26
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• 1985

This study has been carried out to examine into wettability of Cu-5%Sn alloy in $Al_2O_3$, MgO, $SiO_2$ and graphite, respectively and investigated into the change in macrostructure of Cu-5%Sn alloy according to kind and mixing rate of mold-coating. The results obtained from the experiment are summerized as follows; 1. Cu Cu-5%Sn alloy, wettabilities of $Al_2O_3$ and MgO were good, on the other hand, wettabilities of $SiO_2$ and graphite were bad. 2. The fine equiaxed zone was created because of the role of $Al_2O_3$ and MgO as preferential nucleation sites. 3. Notwithstanding change of mixing rate of $SiO_2$ in mold coating the equixed zone was not created. 4. The area of equiaxed zone was varied according to mixing rate in the case of using $Al_2O_3$ and MgO in mold-coating.

• 공업화학
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• 제28권4호
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• pp.437-441
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• 2017

본 연구에서는 방화용 실란트의 첨가제로 사용되는 팽창흑연의 부피팽창률과 경도특성을 개선하기 위해 팽창흑연에 다양한 수지를 코팅한 후 그 특성을 고찰하였다. 수지의 코팅률을 나타내는 평균코팅두께는 수지의 건조속도와 점도의 영향으로 초산비닐계수지 > 아크릴수지 > 우레탄수지 > 수용성라텍스의 순으로 크게 나타났다. 또한 수지의 종류에 따라 코팅된 팽창흑연의 부피팽창률은 우레탄수지 > 수용성라텍스 > 아크릴수지 > 초산비닐계수지의 순으로 컸으며, 경도는 초산비닐계수지 > 아크릴수지 > 수용성라텍스 > 우레탄수지의 순으로 증가함을 알 수 있었다. 이는 코팅처리를 하지 않은 팽창흑연에 비해 부피팽창률은 감소하나 경도가 현저하게 증가되어 방화첨가제로 사용이 가능함을 알 수 있었다. 반응표면분석법에 의한 최적화실험 결과 아크릴수지의 최적코팅 조건은 수지의 첨가량 37.6 wt%과 코팅 교반속도 441.4 rpm이었다.