원자력플랜트 고온구조용 SiC<SUB>f</SUB>/SiC 복합재료의 기계적 특성 평가

윤한기(Han-Ki Yoon),조호준(Ho-Jun Cho),박원조(Won Jo Park) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.4

SiC<SUB>f</SUB>/SiC composites are well-known materials for high temperature structural applications because of their intrinsic properties using fusion power reactors such as shield and divertor coolant channel. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiC<SUB>f</SUB>/SiC composite can be considered as a promising for structural materials because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the fiber. Therefore, an improvement of the coating fiber is key requirements for fabrication of SiC<SUB>f</SUB>/SiC composites by LPS method. In this paper, The SiC<SUB>f</SUB>/SiC composites were fabricated by the LPS method and investigated effects of SiC fiber coating. The SiC<SUB>f</SUB>/SiC composites were fabricated with coated and uncoated Tyranno-SA fibers. The thickness of the coating fiber was 0.25 ㎛ and 0.5 ㎛. In order to investigate effects of coating, the flexural strength were carried out at room temperature, respectively. The densification and microstructure of LPS-SiC<SUB>f</SUB>/SiC composites were observed by FE-SEM.

보강재에 도금된 Cu층이 Al/SiC복합재료의 젖음성에 미치는 영향

이경구,조규종,이도재,Lee, Gyeong-Gu,Jo, Gyu-Jong,Lee, Do-Jae 한국재료학회 2001 한국재료학회지 Vol.11 No.5

SiC 보강재 표면에 도금된 Cu금속층이 Al/SiC복합재료의 젖음성에 미치는 영향을 검토하였다. 보강재에 대한 금속층의 도금은 무전해도금법을 이용하였으며, Al/SiC 복합재료의 제조는 텅스텐 발열체 진공로의$ 670^{\circ}C$~$900^{\circ}C$에서 제조하여 보강재와 기지간의 접촉부위를 촬영하여 젖음성을 측정하였다 젖음성 측정 결과 보강재에 도금된 Cu층은 젖음성을 향상시켰고, 젖음성의 개선은 보강재에 도금된 금속층과 기지간의 반응에 의해 계면에너지를 변화시킴으로서 나타난 결과이며. 반응을 통한 산화피막의 배제도 영향을 미친 것으로 판단된다 Effects of coating treatment of metallic Cu film on SiC for Al/SiC composite were studied. The Copper was deposited on SiC by electroless plating method. Al/sic composite was fabricated at temperature range of $670^{\circ}C$ to 90$0^{\circ}C$ under vacuum atmosphere. The wetting behavior of Al/SiC composite were analysed by SEM and XRD. The coating treatment on SiC improved wettability of Al melt on SiC considerably comparing to the non coated SiC. This improved wettability seems strongly concerned to the increase of chemical reactivity between coated layer and Al matrix. The improvement of wettability of Al melt on the Cu coated SiC was closely related to in the initial stage of reaction. The metallic film played an important role in reducing the interfacial free energy and breaking down the aluminum oxide film through the reaction with Al melt. The wetting behavior of the as-received SiC with Al melt was not uniform, indicated by the contact angles from less than $97^{\circ}$to more than $97^{\circ}$.

서브마이크론/나노 크기의 SiC 비율변화에 따른ZrB2-SiC 세라믹스의 열적, 기계적 특성

김성원,채정민,이성민,오윤석,김형태,정승부 한국세라믹학회 2013 한국세라믹학회지 Vol.50 No.6

ZrB2-SiC ceramics are fabricated via hot pressing with different ratios of submicron or nano-sized SiC in a ZrB2-20 vol%SiC system, in order to examine the effect of the SiC size ratio on the microstructures and physical properties, such as thermal conductivity,hardness, and flexural strength, of ZrB2-SiC ceramics. Five different ZrB2-SiC ceramics (ZrB2-20 vol%[(1-x)SiC + xnanoSiC] where x = 0.0, 0.2, 0.5, 0.8, 1.0) are prepared in this study. The mean SiC particle sizes in the sintered bodies are highly dependent on the ratio of nano-sized SiC. The thermal conductivities of the ZrB2-SiC ceramics increase with the ratio of nano-sized SiC, which is consistent with the percolation behavior. In addition, the ZrB2-SiC ceramics with smaller mean SiC particle sizes exhibit enhanced mechanical properties, such as hardness and flexural strength, which can be explained using the Hall-Petch relation.

서브마이크론/나노 크기의 SiC 비율변화에 따른 ZrB₂-SiC 세라믹스의 열적, 기계적 특성

김성원,채정민,이성민,오윤석,김형태,Kim, Seongwon,Chae, Jung-Min,Lee, Sung-Min,Oh, Yoon-Suk,Kim, Hyung-Tae 한국세라믹학회 2013 한국세라믹학회지 Vol.50 No.6

$ZrB_2$-SiC ceramics are fabricated via hot pressing with different ratios of submicron or nano-sized SiC in a $ZrB_2$-20 vol%SiC system, in order to examine the effect of the SiC size ratio on the microstructures and physical properties, such as thermal conductivity, hardness, and flexural strength, of $ZrB_2$-SiC ceramics. Five different $ZrB_2$-SiC ceramics ($ZrB_2$-20 vol%[(1-x)SiC + xnanoSiC] where x = 0.0, 0.2, 0.5, 0.8, 1.0) are prepared in this study. The mean SiC particle sizes in the sintered bodies are highly dependent on the ratio of nano-sized SiC. The thermal conductivities of the $ZrB_2$-SiC ceramics increase with the ratio of nano-sized SiC, which is consistent with the percolation behavior. In addition, the $ZrB_2$-SiC ceramics with smaller mean SiC particle sizes exhibit enhanced mechanical properties, such as hardness and flexural strength, which can be explained using the Hall-Petch relation.

나노 SiC 입자의 형상에 따른 탄소섬유 강화 에폭시 복합재료의 기계적 및 계면 물성 변화 관찰

권동준 ( Dong Jun Kwon ),왕작가 ( Zuo Jia Wang ),김제준 ( Je Jun Kim ),장기욱 ( Key Wook Jang ),박종만 ( Joung Man Park ) 한국접착및계면학회 2013 접착 및 계면 Vol.14 No.2

SiC 나노입자를 이용하여 에폭시 복합재료를 제조할 수 있다. SiC 형상에 따른 영향으로 복합재료의 계면 물성이 변화된다. SiC의 형상에 따른 계면 상태의 변화를 관찰하기 위해 베타 형태, 위스커 형태의 SiC 나노입자를 사용하였다. 나노입자에 대한 분산도를 평가하기 위해 커패시턴스를 이용한 분산도 평가방법을 활용하였다. FE-SEM을 이용하여 SiC 나노입자의 활용에 따른 나노복합 재료의 파단면을 관찰하여, 그 강화 효과를 비교 분석하였다. 탄소섬유와 SiC 나노입자가 함유된 에폭시를 이용한 복합재료에 계면 물성을 비교하기 위해 층간전단강도 평가법과 계면전단강도 평가법을 이용하였다. 복합재료의 계면 물성을 강화하기 위해서는 베타 형태의 SiC 나노입자를 활용할 경우가 위스커 입자를 이용한 경우보다 높은 계면 강도를 나타냈다. Epoxy matrix based composites were fabricated by adding SiC nano fillers. The interfacial properties of composites were varied with different shapes of SiC nano fillers. To investigate the shape effects on the interfacial properties, beta and whisker type SiC nano fillers were used for this evaluation. The dispersion states of nano SiC-epoxy nanocomposites were evaluated by capacitance measurements. FE-SEM was used to observe the fracture surface of different structures of SiC-epoxy nanocomposites and to investigate for reinforcement effect. Interfacial properties between carbon fiber and SiC-epoxy nanocomposites were also evaluated by ILSS (interlaminar shear strength) and IFSS (interfacial shear strength) tests. The interfacial adhesion of beta type nanocomposites was better than whisker type.

SiC_f/SiC 복합체의 특성에 미치는 열간가압소결 조건의 영향

노비얀토 알피안,윤당혁,Noviyanto, Alfian,Yoon, Dang-Hyok 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.5

Continuous SiC fiber-reinforced SiC-matrix composites ($SiC_f$/SiC) had been fabricated by electrophoretic infiltration combined with ultrasonication. Nano-sized ${\beta}$-SiC added with 12 wt% of $Al_2O_3-Y_2O_3$ additive and Tyranno$^{TM}$-SA3 fabric were used as a matrix phase and fiber reinforcement, respectively. After hot pressing at 5 different conditions, the density, microstructure and mechanical properties of $SiC_f$/SiC were characterized. Hot pressing at relatively severe conditions, such as $1750^{\circ}C$ for 1 and 2 h, resulted in a brittle fracture behavior due to the strong fiber-matrix interface in spite of their high flexural strength. On the other hand, toughened $SiC_f$/SiC composite could be achieved by hot pressing at milder condition because of the formation of weak interface in spite of the decreased flexural strength. These results proposed the importance of weak fiber-matrix interface in the fabrication of ductile $SiC_f$/SiC composite.

SiC_f/SiC 복합체의 특성에 미치는 열간가압소결 조건의 영향

노비얀토 알피안,윤당혁 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.5

Continuous SiC fiber-reinforced SiC-matrix composites (SiC_f/SiC) had been fabricated by electrophoretic infiltration combined with ultrasonication. Nano-sized β-SiC added with 12 wt% of Al_2O_3-Y_2O_3 additive and Tyranno^(TM)-SA3 fabric were used as a matrix phase and fiber reinforcement, respectively. After hot pressing at 5 different conditions, the density, microstructure and mechanical properties of SiC_f/SiC were characterized. Hot pressing at relatively severe conditions, such as 1750℃ for 1 and 2 h, resulted in a brittle fracture behavior due to the strong fiber-matrix interface in spite of their high flexural strength. On the other hand, toughened SiC_f/SiC composite could be achieved by hot pressing at milder condition because of the formation of weak interface in spite of the decreased flexural strength. These results proposed the importance of weak fiber-matrix interface in the fabrication of ductile SiC_f/SiC composite.

자기파를 함유한 SiCwlf 세라믹스의 미세구조 제어

이성희 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.5

SiC를 51.9wt% 함유한 SiC-자기질 혼합 분말이 자기 코아의 표면연마 공정에서 부산물로 발생한다. 이 원료 분말을 SiC질 세라믹스를 제조하기 위한 출발물질로 하였다. 원료자체로 성형 $1350^{\circ}C$에서 열처리하면 SiC, $Al_{2}O_{3}$, cristoblite, mullite 결정상이 존재하면 미세구조는 SiC 입자를 유리질 매트릭스가 덮고 있고 구형 기공이 존재한다. 원료 성형체를 열처리시 시편 무게 증가에 의해 판단되는 SiC의 산화는 600~$800^{\circ}C$ 범위에서 시작하나 XRD 분석에 의해서는 $1000^{\circ}C$ 열처리에 이르러서야 $SiO_{2}$의 cristobalite 결정상을 확인하였다. 예비 열처리 후에 소성한 시편은 mullite화 반응이 촉진되는데, $1000^{\circ}C$의 예비 열처리 후 $1350^{\circ}C$에서 소성한 시편은 SiC, cristobalite, mullite가 결정상으로 존재하며, 밀도 2.24g/$cm^{3}$, 흡수율 11.73%이고 유리상이 적고 다공성인 미세구조를 갖는다. 원료 자체에서 51.9wt%이던 SiC 함량은 $1350^{\circ}C$ 소성시편에서는 예비 열처리 조건에 따라 약 37~22%로 감소한다. The SiC-porcelain powder mixtures containing 51.9wt% SiC are produced as by-products from the surface abrasion process of porcelain cores. This raw powders were used as starting materials for the synthesis of SiC containing ceramics. The specimen, which was fired at 135$0^{\circ}C$ from raw powders, had SiC, $Al_{2}O_{3}$, , cristobalite, mullite as crystalline phases, and the fractured microstructure showed dispersed SiC crystalline particles almost wetted with glassy matrix and spherical pores. Although the oxidation of SiC containing powder compacts wetted with glassy matrix and spherical pores. Although the oxidation of SiC containing powder compacts started at the range of 600~80$0^{\circ}C$ form the analysis of weight gain, the presence of $SiO_{2}$ crystallien phase and cristobalite was confirmed at 100$0^{\circ}C$ by XRD analysis. Mullitization of specimens was accelerated by preheating before the final firing. The specimen sintered at 135$0^{\circ}C$ after 100$0^{\circ}C$ preheating consisted of SiC, cristobalite, mullite as crystalline phases, and revealed 2.24g/$cm^{3}$ bulk density, 11.73% water adsorption, porous microstructure with small amount of glassy phase. SiC contents of specimens, which was 51.9 wt% in the raw powders, reduced to 37~22 wt% after firing at 135$0^{\circ}C$ depending on the preheating condition.

차세대 핵융합로용 SiC/SiC 복합재료의 개발 및 연구동향

윤한기(Han-Ki Yoon) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.8

Silicon carbide (SiC) materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine, because it has excellent high temperature strength, high elastic modulus, low coefficient of thermal expansion, high heat transfer characteristics, good resistance to oxidation, and good thermal and chemical stability. So that, the present status and future prospects of silicon (SiC) continuous fiber-reinforced SiC-matrix ceramic composites (SiC/SiC composites) is reviewed from the viewpoint of material development for applications to blanket/first wall structures in fusion powder devices and other advanced nuclear systems. In this paper, the current status of SiC/SiC composite R&D for advanced fusion reactor in ITER is introduced.

LPS-SiC 세라믹스 제조특성에 미치는 소결온도의 영향

박이현(Yi-Hyun Park),정헌채(Hun-Chae Jung),김동현(Dong-Hyun Kim),윤한기(Han-Ki Yoon),A. Kohyama 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

SiC materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiC<SUB>f</SUB>/SiC composites can be considered as a promising for various structural materials, because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the reinforcing fiber during the hot pressing. Therefore, reduction of sintering temperature and pressure is key requirements for the fabrication of SiC<SUB>f</SUB>/SiC composites by hot pressing method. In the present work, Monolithic LPS-SiC was fabricated by hot pressing method in Ar atmosphere at 1760 ℃, 1780 ℃, 1800 ℃ and 1820 ℃ under 20 MPa using Al₂O₃ - Y₂O₃ system as sintering additives in order to low sintering temperature. The starting powder was high purity β-SiC nano-powder with an average particle size of 30 ㎚. Monolithic LPS-SiC was evaluated in terms of sintering density, micro-structure, flexural strength, elastic modulus and so on. Sintered density, flexural strength and elastic modulus of fabricated LPS-SiC increased with increasing the sintering temperature. In the micro-structure of this specimen, it was found that grain of sintered body was grown from 30 ㎚ to 200 ㎚.