SiC 의 액상소결에 미치는 변수의 영향 및 이를 이용한 접합 연구

다국어 초록 (Multilingual Abstract)

This study examines the liquid-phase sintering behavior of silicon carbide (SiC) and evaluates a Si-C reaction-based joining technique with the goal of establishing processing guidelines for reliable SiC components used in high-temperature environments. The effects of key sintering parameters-including additive composition, particle size of the sintering additives, sintering atmosphere, pressure schedule and starting-powder characteristics-were systematically investigated. Among the oxide additives considered, the Al2O3-Y2O3 system provided the most stable liquid formation, and compositions near 60:40(Al2O3:Y2O3) produced a well-distributed liquid phase that promoted rapid densification. When pressure was applied after the liquid had fully developed, pore elimination was significantly enhanced and dense microstructures with uniform grain boundaries were achieved. In pressureless sintering, densification relied almost entirely on liquid mobility, and therefore the initial compact density, retention of the liquid phase, and the prevention of additive loss were critical factors. Cold isostatic pressing improved the homogeneity of the green body, while the use ofa powder bed helped maintain the necessary amount of liquid during high-temperature exposure. Densification increased noticeably at 1850-1900°C, whereas excessive volatilization of additives limited further improvement at higher temperatures. The Si-C reaction bonding process was also examined using SiC/C tape fillers of various thicknesses and mixing ratios. Thin and compositionally balanced tapes enabled smooth Si infiltrated and the formation of a continuous reaction layer, resulting in joints that fractured within the SiC substrate rather than the bonded region. Surface-roughness tests showed that even substrates with relatively coarse industrial scale finishes maintained sufficient wettability and bonding strength, demonstrating the robustness of the reaction bonding method.

목차 (Table of Contents)

• 제 1장 서론 1
• 제 2장 이론적 배경 7
• 2.1 탄화규소(silicon carbide, SiC) 7
• 2.2 SiC 소결 11
• 2.2.1 고상소결(Solid-state sintering) 13
• 2.2.2 액상소결(Liquid-phase sintering) 16
• 2.2.2.1 액상 소결조제(Sintering additives) 16
• 2.2.3 가압소결(Hot pressing) 19
• 2.2.4 반응소결(Reaction-bonded sintering) 19
• 2.2.5 Spark Plasma Sintering (SPS) 20
• 2.3 SiC 접합 21
• 2.3.1 고상확산접합(Solid-state diffusion bonding) 21
• 2.3.2 Si-C 반응접합(Si-C reaction bonding) 23
• 2.3.3 유리세라믹 접합(Glass-ceramic bonding) 25
• 2.3.4 NITE 접합(Nano-infiltration and transient eutectic bonding) 26
• 2.3.5 MAX 상 접합(MAX-phase bonding) 27
• 2.3.6 직접 접합(Direct bonding) 30
• 제 3장 실험 방법 31
• 3.1 SiC 액상소결 31
• 3.1.1 출발원료 및 소결조제 31
• 3.1.2 가압 액상소결 35
• 3.1.3 무가압 액상소결 39
• 3.2 SiC 접합 41
• 3.2.1 Si-C 반응접합 41
• 3.2.1.1 패브릭을 이용한 시편 구성. 41
• 3.2.1.2 노치 기반 시편 구성 42
• 3.2.1.3 접합면 조도 조건 시편 준비 42
• 3.2.1.4 접합재 제작 43
• 3.2.1.5 Si 용융 실험 46
• 3.2.2 MAX 상 접합 46
• 3.2.3 NITE 접합 46
• 3.2.4 직접접합 47
• 3.3 특성평가 48
• 3.3.1 상대밀도(Relative density; Archimedes method) 48
• 3.3.2 상 분석(Phase analysis; X-ray diffraction) 48
• 3.3.3 미세구조(Microstructure, SEM) 49
• 3.3.4 기계적 특성(Mechanical properties) 49
• 3.3.5 점도 측정 49
• 제 4장 실험 결과 및 논의 51
• 4.1 액상소결 결과 51
• 4.1.1 소결조제 조성 변화의 영향. 51
• 4.1.2 가압 액상소결에서 변수의 영향 54
• 4.1.3 무가압 액상소결 결과 61
• 4.2 Si-C 반응접합 결과 65
• 4.2.1 Si 용융 실험 65
• 4.2.2 접합재의 영향 68
• 4.2.3 패브릭 기반 접합 75
• 4.2.4 접합면 조도 효과 78
• 4.3 직접접합 결과 82
• 제 5장 결론 84
• References 86