Boron 添加에 따른 炭素材料의 機械的 物性變化 및 酸化擧動 = Mechanical Properties and Oxidation Behavior of Boron Additives Implanted Carbon Materials

다국어 초록 (Multilingual Abstract)

This paper describes the mechanical properties and oxidation resistance of carbon fibers and 2D C/C composites with and without additions of boron additives(boron and boron oxide), and describes the changes in these properties resulting from increased HTT of the composites. In case of carbon fibers, for this experiment, were heat treated up to 1800℃, 2000℃, 2200℃, 2400℃, 2600℃ and 2800℃ each with and without boron coating on the surface of fibers. On the other hand, for invesgigation of 2D carbon/carbon composites, specimen were heat treated up to 1800℃, 2000℃, 2200℃, 2400℃ and 2600℃ with addition of boron in the matrix. and prepared references with same HTT condition without boron addition.
The treatment of boron in carbon fibers below 2200℃ did not show the improvement of tensile strength and modulus except for the improvement of oxidation resistance. and B_2O_3 coating layer more contribute than that of crystallization of carbon fiber in terms of reducing the active sites from oxygenl attacks. In cases of boron-doped carbon fiber above 2600℃, carbon fibers are doped substitutionally with boron, which acceletate the graphitization of carbon fibers.
The addition of boron in matrix showed the decrease of mechanical properties of 2D carbon/carbon composites. but 1% and 3% boron added specimen heat-treated up to 1700℃ and 2000℃ showed the slight increasement of ILSS. It is probably that boron particles bar from the propagation of cracks byt others heat-treated up to 2300℃ and 2600℃ showed no differences between boron added specimen and non-added specimen.
Boron oxide implanted carbon fibers showed more resistant on oxygen attack but what heat-treated below 2200℃ showed almost trend of air oxidation. Although protection barrier B_2O_3 might be formed on the surface of carbon fibers and protect sxygen attack a little bit but boron oxide may not affect the graphitization which is the most important factor for oxidation resistance.
These results described that Heat treatment above 2300℃ resulted in a reaction between the inhibitors and the carbonaceous components of the composites. These reaction affected both fibers and matrix, resulting in almost complete crystallization of the composite components. This crystallization transformed the microstructure of the carbon fibers and composites, weakening them and producing brittle failure behaviour.

목차 (Table of Contents)

• 목차
• I. 서론- = 1
• II. 이론적 고찰 = 3
• 1. 탄소섬유의 구조 및 물성 = 3
• 2. 산화의 관점에서의 탄소물질의 구조 특성 = 7
• 2-1 탄소의 기체화 반응과 반응성 = 7
• 2-2 선택적 기체화 = 7
• 2-3 화학 흡·탈착 이론 = 10
• 3. 페놀수지의 탄화 거동 = 12
• 4. 탄소/탄소 복합재의 기계적 특성 = 13
• 4-1 2D 탄소/탄소 복합재으 파괴 거동 = 13
• 4-2 산화가 탄소/탄소 복합재의 기계적 물성에 미치는 영향 = 15
• 5. boron의 산화 억제 메커니즘 = 16
• 5-1 흑연화의 촉진 = 16
• 5-2 특정 자리 봉쇄를 통한 기체 확산 억제 = 16
• 5-3 탄소와의 치환을 통한 산화 억제 = 18
• 6. 산화억제제의 특성 = 20
• 6-1 boron의 탄소와의 반응 = 20
• 6-2 boron 원소 = 21
• 6-2-1 화학적 성질 = 22
• 6-3 Boron oxide = 22
• 6-3-1 물리적 성질 = 22
• 6-3-2 화학적 성질 = 22
• III. 실험 = 24
• 1. 실험재료 = 24
• 1-1 탄소섬유 = 24
• 1-2 보강재 = 24
• 1-3 매트릭스 전구체 = 25
• 1-4 Boron과 Boron Oxide(산화억제제) = 25
• 2. 시편 제작 = 26
• 2-1 boron산화물이 코팅된 탄소섬유 제작 = 26
• 2-1-1 boron산화물의 코팅 = 26
• 2-1-2 섬유의 열처리 = 26
• 2-2 2D 탄소/탄소 복합재의 제작 = 26
• 2-2-1 페놀수지와 boron원소의 �합 = 26
• 2-2-2 green bodies의 제작 = 27
• 2-2-3 시편으 탄화 및 열처리 = 27
• 3. 시험 및 분석 = 29
• 3-1 밀도 측정 = 29
• 3-2 정량분석(ICP test) = 29
• 3-3 ILSS, 파괴강도 및 굴곡 모듈러스 측정 = 29
• 3-4 열 중량 분석 (TGA) = 29
• 3-5 결정화도 분석 (XRD) = 30
• IV. 결과 및 고찰 = 31
• 1. 탄소섬유 = 31
• 1-1 XRD 분석 = 31
• 1-2 Tensile strength 및 modulus 측정 = 35
• 1-3 TGA 분석(탄소섬유) = 38
• 2. 2D 탄소/탄소 복합재 = 41
• 2-1 밀도 분석 및 ICP 테스트 결과 = 41
• 2-2 기계적 물성 시험 = 43
• 2-3 기계적 물성변화 메카니즘 = 44
• 2-4 TGA 분석 = 48
• 2-5 XRD 분석 = 50
• V. 결론 = 58
• VI. 참고문헌 = 59