• Advanced Composite Materials
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• 제18권1호
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• pp.61-75
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• 2009

The effect of porous matrix on thermal fatigue behavior of 3D-orthogonally woven SiC/SiC composite was evaluated in comparison with that having relatively dense matrix. The porous matrix yields open air passages through its thickness which can be utilized for transpiration cooling. On the other hand, the latter matrix is so dense that the air passages are sealed. A quantity of the matrix was varied by changing the number of repetition cycles of the polymer impregnation pyrolysis (PIP). Strength degradation of composites under thermal cycling conditions was evaluated by the $1200^{\circ}C$/RT thermal cycles with a combination of burner heating and air cooling for 200 cycles. It was found that the SiC/SiC composite with the porous matrix revealed little degradation in strength during the thermal cycles, while the other sample showed a 25% decrease in strength. Finally it was demonstrated that the porous structure in 3D-SiC/SiC composite improved the thermal fatigue durability.

• 한국세라믹학회지
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• 제51권5호
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• pp.430-434
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• 2014

$SiC_f$/SiC composites were prepared using the hybrid process of chemical vapor infiltration (CVI) and polymer impregnation and pyrolysis (PIP). Before the application of PIP, partially matrix-filled preform composites with different densities were fabricated by control of chemical vapor infiltration time and temperature. The changes of the final density of the $SiC_f$/SiC composites had a tendency similar to that of preform composites partially filled by CVI. Composites with lower density after the CVI process had a larger increment of density during the PIP process. Three types of microstructures were observed on the fractured surface of the composite: 1) well pulled-out fibers and lower density, 2) slightly pulled-out fibers and higher density, and 3) only bulk SiC. The different fractions and distributions of the microstructures could have an effect on the mechanical properties of the composites. In this study, $SiC_f$/SiC composites prepared using a hybrid process of CVI and PIP had density values in the range of $1.05{\sim}1.44g/cm^3$, tensile strength values in the range of 76.4 ~ 130.7 MPa, and fracture toughness values in the range of $11.2{\sim}13.5MPa{\cdot}m^{1/2}$.

• 폴리머
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• 제33권6호
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• pp.575-580
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• 2009

폴리카보실란에 탄소직물을 보강제로 이용하여 제조한 탄소/탄화규소 복합재는 좋은 내산화 특성과 열 충격에 강한 특성으로 인해 높은 온도의 구조체에 적용되고 있다. 본 연구에서는 고분자 함침 열분해법을 이용하여 탄소직물에 폴리카보실란 용액을 함침한 후, 전자선을 이용하여 가교하고, 열분해 과정을 통해 탄소/탄화규소 복합재로 제조하였다. 실험 결과 복합재 시료의 공극률과 밀도는 각각 13.5%와 $2.44\;g/cm^3$을 나타냈고, 내산화 특성은 지속적인 고온의 산화 분위기에서 95.9%의 잔류량을 나타내어 본 연구에서 제조한 탄소/탄화규소 복합재의 우수한 내산화 특성을 확인하였다.

• 한국표면공학회지
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• 제50권6호
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• pp.523-530
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• 2017

In this study, we developed the h-BN interphase for ceramic matrix composites (CMCs) through a wet chemical coating method, which has excellent price competitiveness and is a simple process as a departure from the existing high cost chemical vapor deposition method. The optimum condition for nitriding an h-BN interphase using boric acid and urea as precursors were derived, and the h-BN interphase coating through a wet method on a carbon preform of 2.5 D was conducted to apply the optimum conditions to the CMCs. In order to control the coating property via the wet coating method, four parameters were investigated such as dipping time of the specimen in the precursor solution, the ratio of boric acid and urea in the precursor, the concentration of solution where the precursor was dissolved, and the cycle of dipping and dry process. The CMCs was fabricated through polymer impregnation and pyrolysis (PIP) processes and a three-point flexural strength test was conducted to verify the role of the coated h-BN interphase.

• Composites Research
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• 제29권1호
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• pp.40-44
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• 2016

원자력발전소에서 사용되고 있는 핵연료 피복관은 핵분열 생성물들의 외부 유출을 방지하기 위해 고온 고압의 냉각수 분위기에서 우수한 산화저항성을 가져야 한다. 그러나 후쿠시마 원전사고의 LOCA(Loss-Of-Coolant-Accident)와 같은 중대사고에서 핵연료의 피복관과 수증기 사이의 격렬한 반응으로 인해 급격한 고온산화를 동반한 다량의 수소발생으로 수소폭발을 방지하기 위한 핵연료의 개발이 요구되고 있다. 이에 따라 핵연료 피복관의 안전성 향상을 위해 내방사선성이 우수하며 높은 강도와 산화, 부식에 대한 내화학적 안정성 및 우수한 열전도도 의 특성을 갖는 SiC와 같은 구조용 세라믹스가 활발히 연구되고 있다. $SiC_f/SiC$ 복합체 보호막 금속 피복관은 지르코늄 피복관 튜브에 SiC 섬유를 필라멘트 와인딩 한 후 Polycarbosilane을 polymer로 함침하여 기지상을 형성하는 공정을 이용하였다. 따라서 이렇게 제조한 $SiC_f/SiC$ 복합체 금속 피복관을 Drop Tube Furnace를 이용한 열충격에 따른 시편의 산화 및 미세조직을 분석하였다.