표제지
초록
목차
제1장 서론 14
제2장 연구 배경 및 연구 목적 18
2-1. 경사기능 재료(Functionally Gradient Materials : FGM) 18
1. 화학 증착법(CVD) 20
2. 분말 야금법(Powder Metallurgy) 20
3. 플라즈마 용사법(Plasma Spraying) 21
4. 자전 고온 반응 합성법(Self-propagating High-temperature Synthesis : SHS) 22
2-2. 방향성 금속 산화법(Directed Metal Oxidation : DIMOX™, Lanxide Co., USA) 23
(1) 초기 산화단계(Initial Oxidation) 27
(2) 반응 지체구간(Incubation Period) 27
(3) 체적 산화구간(Bulk Oxidation) 27
제3장 직접 질화법에 의한 경사 기능 재료의 제조 30
3-1. 서언 30
3-2. 실험방법 32
3-3. 실험결과 및 고찰 34
3-3-1. 질화 반응의 TG-DTA 분석 34
3-3-2. 첨가제 AIN의 함량이 질화 반응 두께에 미치는 영향 36
3-3-3. 예비소결에 의한 재료의 치밀화 44
3-3-4. 마그네슘의 첨가량과 분말의 크기가 질화 반응에 미치는 영향 50
3-4. 결언 52
제4장 직접 산화법에 의한 경사기능 재료의 제조 53
4-1. 서언 53
4-2. 실험방법 및 실험장치 56
4-2-1. 원료 분말 및 분말 성형체 제조 56
4-2-2. TGA 장치의 반응 조건 57
4-2-3. 반응층의 특성 분석 59
4-3. 실험결과 및 고찰 60
4-3-1. 반응층의 미세구조 62
4-3-2. 반응 시차 중량 분석 (TGA : Thermogravimetric Analysis) 73
4-3-3. 반응 시차에 따른 반응층의 미세구조 변화[내용누락;p.81] 86
4-3-4. 반응 메커니즘 95
4-4. 결언 103
제5장 결론 105
참고 문헌 108
ABSTRACT 114
Table 3-1. The reaction layer thicknesses with AIN contents added differently 41
Table 3-2. Effect of presintering on the density of the reaction product.(Al particle size was 5㎛ and Mg content was 4wt%) 44
Table 3-3. The reaction layer thicknesses with different Mg contents. 51
Table 4-1.Characteristics of the raw materials 56
Table 4-2. The content of Mg on the surface of the sample reacted at 900℃ for 10 min. The content was measured at different... 98
Fig. 2-1. Characteristic of FGM 19
Fig. 2-2. Fabrication process of FGM by powder metallurgy 21
Fig. 2-3. (a) Directed Metal Oxidation Process (b) Microstructure of the Al₂O₃/Al composite... 25
Fig. 2-4. The reaction stages of the DIMOX process 26
Fig. 2-5. The microstructural change according to the reaction stage of DIMOX process 28
Fig. 3-1. Schmatic drawing of nitridation apparatus 33
Fig. 3-2. TG-DTA result of Al-4wt%Mg powder mixture under nitrogen atmosphere 35
Fig. 3-3. Cross sectional appearances of the samples after reaction at 900℃ for 4hours. 38
Fig. 3-4. Optical micrograph of the sample reacted at 900℃ for 4 hours 39
Fig. 3-5. Profile of micro vickers hardness from the surface 42
Fig. 3-6. Micro vickers hardness variations in samples with different amounts of AlN added. 43
Fig. 3-7. SEM micrographs of the samples after the reaction at 900℃ for 4 hours. 47
Fig. 3-8. A X-ray diffraction pattern of the reaction layer. (Al-8wt%Mg FGM) 48
Fig. 3-9. SEM micrograph of the fractured surface at the metalrich portion of the sample. 49
Fig. 4-1. Schematic drawing of TGA(thermogravimetric) system 58
Fig. 4-2. Shape of specimen before and after reaction 60
Fig. 4-3. Optical micrograph of reaction layer 63
Fig. 4-4. SEM micrograph of reaction layer 64
Fig. 4-5. (a) Microstructure of dense ceramic layer (b) Fractured surface of dense ceramic layer 67
Fig. 4-6. (a) The content of metallic Al in the reaction layers of each type of the samples. 71
Fig. 4-6. (b) The variation of the microhardness in the rection layers of each type of the samples. 72
Fig. 4-7. Mutual relationship between the growth of reaction layer and the weight gain of specimen. 75
Fig. 4-8. Effect of reaction temperature on the oxidation behavior. 78
Fig. 4-9. Effect of the gas flow rate on the oxidation behavior. 79
Fig. 4-10. Effect of Mg content on the oxidation behavior. 81
Fig. 4-11. Effect of Mg content on the thickness of reaction layer. 82
Fig. 4-12. Effect of the Al₂O₃ content on the oxidation behavior. 84
Fig. 4-13. Effect of the Al₂O₃ content on the thickness of reaction layer. 85
Fig. 4-14. (a) The weight gain of the each samples as a function of reaction time. (reaction temperature : 900℃) 89
Fig. 4-14. (b) The total thickness of the reaction layers of each samples with various reaction time. (reaction temperature : 900℃) 90
Fig. 4-15. SEM micrographs of the sample.(Al-7wt%Mg+10wt%Al₂O₃) 93
Fig. 4-17. XRD pattern of the surface of the reaction layer. (reacted at 900℃ for 10 min.) 97
Fig. 4-18. SEM micrograph of the MgO layer at the reaction layer surface 98
Fig. 4-19. The growth stage of reaction layer 99
Fig. 4-20. Schematic model illustrating the growth mechanism of reaction layer. 102