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브레이징 접합공정 조건이 SiN<sub>4</sub>/S.S. 316 접합체의 기계적 특성 및 신뢰도에 미치는 영향
장희석,박상환,최성철,Chang, Hwi-Souck,Park, Sang-Whan,Choi, Sung-Churl 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.10
활성 금속 브레이징법의 공정변수인 브레이징 온도 및 시간의 변화가 Cu buffer layer를 사용한 $Si_3N_4$Stainless steel 316 접합체의 기계적 특성 및 신뢰도에 미치는 영향을 규명하기 위하여 브레이징 조건 변화에 따른 접합계면 미세구조 변화를 조사하였다. 900${\circ}C$ 이상의 온도에서 브레이징 된 접합체에서는 Cu buffer layer가 브레이징 합금에 용해되어 연속 Cu층을 유지하지 못하였으며, $Si_3N_4$/brazing alloy 계면에서 계면 반응물 층의 두계도 급격히 증가하였다. 950${\circ}C$에서 브레이징된 Cu buffer layer를 사용한 $Si_3N_4$/Stainless steel 316 접합체의 파괴강도는 접합체 내 잔류응력의 증가로 급격히 감소하였다. 950${\circ}C$ 이하의 온도에서 브레이징 시간의 변화는 Cu buffer layer를 사용한 $Si_3N_4$/Stainless steel 316 접합체의 파괴강도 및 파괴경로에 큰 영향을 미치지 못하였다. The microstructure change of brazed $Si_3N_4$/Stainless steel 316 joint with Cu buffer layer were examined to clarify the effects of brazing process conditions such as brazing time and temperature on the mechanical properties and reliability of brazed joints. For the brazed joint above 900${\circ}C$, the Cu buffer layer was completely dissolved into brazing alloy and the thickness of reaction product formed at $Si_3N_4$/brazing alloy joint interface was abruptly increased, which could increase the amounts of residual stress developed in the joint. The fracture strength of brazed $Si_3N_4$/Stainless steel 316 joint with Cu buffer layer at 950${\circ}C$ was much reduced comparing to those of joints brazed at the lower temperature. But, it was found that the effects of brazing time was not critical on the mechanical properties as well as the reliability of $Si_3N_4$/Stainless steel 316 joint with Cu buffer layer brazed at the temperature below 900${\circ}C$.
황성식,박상환,한재호,한경섭,김찬목,Hwang, Sung-Sic,Park, Sang-Whan,Han, Jae-Ho,Han, Kyung-Sop,Kim, Chan-Mook 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.10
차세대 발전 시스템에서 사용되는 고온 가스 필터용 지지층 소재를 제조하기 위하여 용융 Si 침윤 방법으로 기공율이 32∼36%, 주기공 크기가 37∼90 ${\mu}m$ 범위를 갖는 고강도 다공질 반응소결 탄화규소(RBSC)를 개발하였다. 반응소결 탄화규소 다공체의, 최대 파괴강도는 120MPa이었으며, 용융 Si 침윤 방법으로 제조된 반응소결 탄화규소 다공체에서는 SiC 입자 사이에 SiC/Si로 이루어진 기지상이 형성되어 있기 때문에 파괴 강도 및 열충격 특성이 점토 결합 탄화규소 다공체 보다 우수하였다. 반응소결 탄화규소 다공체의 기공율 및 기공 크기는 잔류 Si의 양 및 성형체에 사용한 SiC 입자 크기에 따라 다르게 나타났다. Porous reaction bonded SiC with high fracture strength was developed using Si melt infiltration method for use of the support layer in high temperature gas filter that is essential to develop the next generation power system such as integrated gasification combined cycle system. The porosity and pore size of porous RBSC developed in this study were in the range of 32∼36% and 37∼90 ${\mu}m$ respectively and the maximum fracture strength of porous RBSC fabricated was 120 MPa. The fracture strength and thermal shock resistance of porous RBSC fabricated by Si melt infiltration were much improved compared to those of commercially available porous clay bonded SiC due to the formation of the strong SiC/Si interface between SiC particles. The characteristics of pore structure of porous RBSC was varied depending on the amounts of residual Si as Well as the size of SiC particle used in green body.
SiC Fiber 강화 다공질 반응 소결 탄화규소 Composite의 제조 및 기계적 특성
한재호,박상환,Han, Jae-Ho,Park, Sang-Whan 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.8
In this study, chopped Hi-Nicalon SiC fiber Reinforced Porous Reaction Bonded SiC (RBSC) composites and it fabrication process were developed by using Si melt infiltration process. The porosity and average pore size in fabricated chopped SiC fiber reinforced porous RBSC composites were in the range of $30{\sim}40%$ and $40-90{\mu}m$, which mainly determined by the SiC powder size used as starting material and amount of residual Si in porous composites. The maximum flexural strength of chopped SiC fiber reinforced porous RBSC composite was as high as 80 MPa. The delayed fracture behavior was observed in chopped SiC fiber reinforced porous RBSC composites upon 3-point bending strength test.
C/Si 몰 비가 TEOS와 페놀수지를 출발원료 사용하여 합성된 β-SiC 분말의 특성에 미치는 영향
염미래,박상환,김영욱,Youm, Mi-Rae,Park, Sang-Whan,Kim, Young-Wook 한국세라믹학회 2013 한국세라믹학회지 Vol.50 No.1
${\beta}$-SiC powders were synthesized by a carbothermal reduction process using $SiO_2$-C precursors fabricated by a sol-gel process using phenol resin and TEOS as starting materials for carbon and Si sources, respectively. The C/Si molar ratio was selected as an important parameter for synthesizing SiC powders using a sol-gel process, and the effects of the C/Si molar ratio (1.4-3.0) on the particle size, particle size distribution, and yield of the synthesized ${\beta}$-SiC powders were investigated. It was found that (1) the particle size of the synthesized ${\beta}$-SiC powders decreased with an increase in the C/Si molar ratio in the $SiO_2$-C hybrid precursors, (2) the particle size distribution widened with an increase in the C/Si molar ratio, and (3) the yield of the ${\beta}$-SiC powder production increased with an increase in the C/Si molar ratio.
β-SiC 분말 Seeds가 Sol-gel 공정으로 합성된 고순도 β-SiC 분말 형상 및 크기에 미치는 영향
김규미,조경선,박상환,Kim, Gyu-Mi,Cho, Gyoung-Sun,Park, Sang-Whan 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.5
High purity $\beta$-SiC powders were synthesized using sol-gel processing. TEOS and phenol resin were used as the starting material for the silicon source and carbon source, respectively. The process turned out to be capable of producing high purity SiC powder purity degree with 99.98 %. However, it was difficult to control the shape and size of $\beta$-SiC powders synthesized by sol-gel process. In this study, $\beta$-SiC powder with size of $1{\sim}5$ um an 30 nm were used as the seeds for $\beta$-SiC to control the $\beta$-SiC powder morphology. It was found that $\beta$-SiC powder seeds was effective to increase the powder average size of synthesized $\beta$-SiC using sol-gel process by acting as the preferred growing sites for $\beta$-SiC.
다층 기공구조를 갖는 다공성 반응소결 탄화규소 다공체 제조
조경선,김규미,박상환,Cho, Gyoung-Sun,Kim, Gyu-Mi,Park, Sang-Whan 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.5
Reaction Bonded Silicon Carbide(RBSC) has been used for engineering ceramics due to low-temperature fabrication and near-net shape products with excellent structural properties such as thermal shock resistance, corrosion resistance and mechanical strength. Recently, attempts have been made to develop hot gas filter with gradient pore structure by RBSC to overcome weakness of commercial clay-bonded SiC filter such as low fracture toughness and low reliability. In this study a fabrication process of porous RBSC with multi-layer pore structure with gradient pore size was developed. The support layer of the RBSC with multi-layer pore structure was fabricated by conventional Si infiltration process. The intermediate and filter layers consisted of phenolic resin and fine SiC powder were prepared by dip-coating of the support RBSC in slurry of SiC and phenol resin. The temperature of $1550^{\circ}C$ to make Si left in RBSC support layer infiltrate into dip-coated layer to produce SiC by reacting with pyro-carbon from phenol resin.