• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.6
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• pp.215-219
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• 2016

Vanadium-doped SiC crystals have been grown by using a porous graphite inner crucible filled with vanadium carbide (VC) and by using a porous graphite plate and SiC + VC powders, respectively. Semi-insulating SiC crystals were grown onto the 6H-SiC seed crystals by PVT (Physical Vapor Transport) method. The grown crystals were indicated to be 6H-SiC polytype by XRD. As result of SIMS analysis, vanadium-rich precipitates were observed when the vanadium concentration was relatively higher than the maximum solubility of vanadium ($3-5{\times}10^{17}cm^{-3}$) in vanadium-doped SiC crystals, which resulted in degradation of crystal quality.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.113.2-113.2
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• 2010

세라믹 필터는 여러 종류의 분진제거 시스템에서 연소 배가스 정제를 위한 가장 적절한 소재로 알려져 있다. 현재까지 다양한 형태의 세라믹 필터가 개발되고 있는데, 캔들 타입(candle type), 튜브 타입(tubular type), 평판 타입(parallel flow type) 등이 그 예이다. 통상적으로 세라믹 캔들 필터는 가압유동층복합발전(PFBC, Pressurize Fluidized-Bed Combustion), 석탄가스화복합발전(IGCC, Integrated coal Gasification Combined Cycle), 석탄가스화연료전지복합발전(IGFC, Integrated coal Gasification Fuel cell Combined cycle)에서 고온 배가스 정제용으로 사용되고 있다. 일반적으로 IGCC나 CTL 합성가스 정제시스템의 경우에는 높은 고압(약 25기압)과 미세분진이 함유되어 있는 분위기에서 운전된다. 그러므로 이때 사용되는 초청정용 세라믹 집진필터는 고온, 고압 및 부식 환경에서 50 MPa 이상을 갖는 높은 강도와 내식성을 갖도록 개발되어야 하기 때문에 SiC(Silicon Carbide)가 가장 적절한 캔들 필터 소재로 적용되고 있다. 이에 따라 집진용 SiC 세라믹 캔들 필터를 개발하기 위해서는 고온에서 내산화성이 우수하고, 부피팽창에 의한 균열이 발생하지 않는 무기결합재의 선정 및 이를 통한 소재의 특성 최적화가 가장 중요한 부분이라 할 수 있다. 본 연구에서는 래밍성형 공정을 적용하여 1m급 탄화규소 세라믹 캔들 필터 시작품을 제조하였으며, 래밍성형 공정 이외에 정수압가압성형, 진공압출성형으로 제조되고 있는 세라믹 캔들 필터의 국내외 시장 및 그 전망을 분석하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.109.2-109.2
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• 2010

세라믹 필터는 여러 종류의 분진제거 시스템에서 연소 배가스 정제를 위한 가장 적절한 소재로 알려져 있다. 현재까지 다양한 형태의 세라믹 필터가 개발되고 있는데, 캔들 타입(candle type), 튜브 타입(tubular type), 평판 타입(parallel flow type) 등이 그 예이다. 통상적으로 세라믹 캔들 필터는 가압유동층복합발전(PFBC, Pressurize Fluidized-Bed Combustion), 석탄가스화복합발전(IGCC, Integrated coal Gasification Combined Cycle), 석탄가스화연료전지복합발전(IGFC, Integrated coal Gasification Fuel cell Combined cycle)에서 고온 배가스 정제용으로 사용되고 있다. 일반적으로 IGCC나 CTL 합성가스 정제시스템의 경우에는 높은 고압(약 25기압)과 미세분진이 함유되어 있는 분위기에서 운전된다. 그러므로 이때 사용되는 초청정용 세라믹 집진필터는 고온, 고압 및 부식 환경에서 50 MPa 이상을 갖는 높은 강도와 내식성을 갖도록 개발되어야 하기 때문에 SiC(Silicon Carbide)가 가장 적절한 캔들 필터 소재로 적용되고 있다. 이에 따라 집진용 SiC 세라믹 캔들 필터를 개발하기 위해서는 고온에서 내산화성이 우수하고, 부피팽창에 의한 균열이 발생하지 않는 무기결합재의 선정 및 이를 통한 소재의 특성 최적화가 가장 중요한 부분이라 할 수 있다. 본 연구에서는 IGCC나 CTL 공정에 적용하기 위한 SiC 캔들 필터 소재 개발을 위해 래밍성형 공정으로 1m급의 탄화규소 캔들 필터 시작품을 제작하여 SiC 출발입자 크기와 무기계 결합재인 스트론튬 카보네이트의 첨가량 변화에 따른 필터 소재의 특성 평가를 수행하였다.

• Journal of Surface Science and Engineering
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• v.49 no.1
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• pp.104-109
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• 2016

Graphite's thermal stability facilitates its widespread use as crucibles and molds in high temperatures processes. However, carbon atoms can be rather easily detached from pores and outer surfaces of the graphite due to the weak molecular force of the c axis of graphites. Detached carbon atoms are known to become a source of dust during fabrication processes, eventually lowering the effective yield of products. As an effort to reduce these problems of dust scattering, we have fabricated SiC composites by employing Si vapor infiltration method into the pores of graphites. In order to understand the diffusion process of the Si vapor infiltration, Si and C atomic percentages of fabricated SiC composites are carefully measured and the diffusion law is used to estimate the diffusion coefficient of Si vapor. A quadratic equation is obtained from the experimental results using the least square method. Diffusion coefficient of Si vapor is estimated using this quadratic equation. The result shows that the diffusion length obtained through the Si vapor infiltration method is about 10.7 times longer than that obtained using liquid Si and clearly demonstrates the usefulness of the present method.

• Journal of the Korean Ceramic Society
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• v.20 no.3
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• pp.199-204
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• 1983

An attempt was made to study wetting behavior of various low temperature molten frist on ceramic substrates including high alumina silicon carbide and porous fired clay plates by Sessile-drop method. The cosine values of contact angles between substrates and molten frist were linear as a function of temperature unless chemical reactions between substrate and molten frit occured. Addition of BaO to frit composition indicated that cosine of values of contact angles were gradually increased with increasing temperature but in the frist contained $Li_2O$ consine values were abruptly increased with increasing temperature after reached a certain temperature. The contact angle increased with increasing roughness of the substrate surface in case of alumina substrate plate.

• Journal of Hydrogen and New Energy
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• v.25 no.4
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• pp.419-424
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• 2014

Direct ethanol fuel cell has been fabricated with ceramic membrane. A porous silicon carbide (SiC) membrane having approximately 30% porosity has been applied for a direct ethanol proton exchange membrane (DE-PEM) fuel cell. A horizontal type cell having Pt ($18mg/cm^2$) catalyst layer on both side of the ceramic membrane was used for the demonstration test. The ethanol oxidation based-fuel cell stack showed very high voltage (1.289V) and measurable current level (68mA) even though at room temperature.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.101-102
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• 2006

Processing techniques for producing microcellular silicon carbide, mullite, and cordierite ceramics have been developed by a reaction method that incorporates a polysiloxane and reactive fillers. The techniques developed in this study offer substantial flexibility for producing microcellular ceramics whereby cell size, cell density, degree of interconnectivity, composition, and porosity can all be effectively controlled. It is demonstrated that the adjustment of filler composition enables the possibility of tailoring the composition and properties of the microcellular ceramics. The present results suggest that the proposed novel processing techniques are suitable for the manufacture of microcellular ceramics with high morphological uniformity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.576-583
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• 2018

Silicon carbide is considered to be a potentially useful material for high-temperature electronic devices, as its band gap is larger than that of silicon and the p-type and/or n-type conduction can be controlled by impurity doping. Particularly, porous n-type SiC ceramics fabricated from ${\beta}-SiC$ powder have been found to show a high thermoelectric conversion efficiency in the temperature region of $800^{\circ}C$ to $1000^{\circ}C$. For the application of SiC thermoelectric semiconductors, their figure of merit is an essential parameter, and high temperature (above $800^{\circ}C$) electrodes constitute an essential element. Generally, ceramics are not wetted by most conventional braze metals,. but alloying them with reactive additives can change their interfacial chemistries and promote both wetting and bonding. If a liquid is to wet a solid surface, the energy of the liquid-solid interface must be less than that of the solid, in which case there will be a driving force for the liquid to spread over the solid surface and to enter the capillary gaps. Consequently, using Ag with a relatively low melting point, the junction of the porous SiC semiconductor-Ag and/or its alloy-SiC and/or alumina substrate was studied. Ag-20Ti-20Cu filler metal showed promise as the high temperature electrode for SiC semiconductors.

• Korean Journal of Materials Research
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• v.27 no.9
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• pp.471-476
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• 2017

In order to improve the high temperature oxidation resistance and lifespan of mat type porous carbon insulation, SiC was coated on carbon insulation by solution coating using polycarbosilane solution, curing in an oxidizing atmosphere at $200^{\circ}C$, and pyrolysis at temperatures up to $1200^{\circ}C$. The SiOC phase formed during the pyrolysis process was converted into SiC crystals as the heat treatment temperature increased, and a SiC coating with a thickness of 10-15 nm was formed at $1600^{\circ}C$. The SiC coated specimen showed a weight reduction of 8.6 % when it was kept in an atmospheric environment of $700^{\circ}C$ for 1 hour. On the other hand, the thermal conductivity was 0.17 W/mK, and no difference between states before and after coating was observed at all.

• Journal of the Korean Ceramic Society
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• v.46 no.5
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• pp.467-471
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• 2009

Effects of boron and carbon on the densification and thermal decomposition of an AlN-SiC-$TiB_2$ system were investigated. $SiO_2$ was mostly removed by the addition of carbon, while $Al_2O_3$ formed $Al_4O_4C$ and promoted the densification of the systems above $1850^{\circ}C$. Rather porous specimens were obtained without the additives after hot pressing at $2100^{\circ}C$, while densification was mostly completed at $2000^{\circ}C$ by using the additives. The sintering temperature decreased further to $1950^{\circ}C$ by applying spark plasma sintering. The additives promoted the shrinkage of AlN by forming a liquid phase which was originated from the carbo- and boro-thermal reduction of $Al_2O_3$ and AlN.