臺灣博碩士論文加值系統

氧化鋁/鎳複合粉末以離子交換法製備。氧化鋁顆粒表面可被微細的金屬鎳顆粒所均勻覆蓋。其中金屬鎳顆粒尺寸小於60 nm。氧化鋁/鎳複合材料在CO氣氛中以無壓燒結後製備。基地相的晶粒成長及複合材料的密度皆因為鎳顆粒的出現而降低。複合材料的彎曲強度因為微結構的細化而增加。複合材料的破裂韌性藉由添加鎳顆粒所導致的裂紋架橋及裂紋偏折機構而增強。氧化鋁/鎳複合材料的氧化作用包含兩個反應：(1)鎳和氧反應形成氧化鎳，(2)鎳及氧化鋁和氧反應形成鎳鋁尖晶石。氧化鎳的形成只在氧化作用的初期發生，而鎳鋁尖晶石的形成卻在氧化作用中持續進行。

The Al2O3/Ni composite powder is prepared by an ion-exchange method. The surface of alumina can be covered uniformly with fine metallic nickel particles. The size of the metallic nickel particle is below 60 nm. After pressureless sintering in CO atmosphere, the Al2O3/Ni composites are prepared. The grain growth of matrix is inhibited and the density of the composites is decreased due to the presence of nickel inclusions. The flexural strength of composites is enhanced by the refinement of microstructure. The fracture toughness of composites is enhanced by the addition of nickel inclusions through crack bridging and crack deflection mechanisms. The oxidation of Al2O3/Ni composites involves two reactions: (1) nickel reacts with oxygen to form nickel oxide, (2) nickel and alumina react with oxygen to form NiAl2O4. The formation of nickel oxide only occurs at the beginning of oxidation, however the formation of NiAl2O4 proceeds continually during the oxidation.

CHAPTER 1 INTRODUCTION……………………………………………..1
CHAPTER 2 LITERATURE SURVRY……………………………………3
2-1 The Ceramic Matrix Composites…………………………………………………3
2-1-1 Inhibition of Grain Growth by Second-Phase Particles……………………..3
2-1-1-1 Zener-type Models……………………………………………………...3
2-1-1-2 Topological Pinning Model……………………………………………..6
2-1-2 The Effect of Microstructure………………………………………………...7
2-1-2-1 The Effect of Porosity…………………………………………………..7
2-1-2-2 The Effect of Grain Size………………………………………………..9
2-1-3 Interfacial Characteristics of composites…………………………………..10
2-1-4 The Toughening Mechanisms of Ceramic Matrix Composites………….…12
2-1-4-1 Crack Bridging Toughening Mechanism…………………...…………16
2-1-4-2 Crack Deflection Mechanism…………………………………………18
2-2 Oxidation……………………………………………………..…………………20
2-2-1 Reactions of Oxidation……………………………………………………..20
2-2-2 Oxidation Mechanism of Al2O3/Ni Composites……………………………20
2-2-2-1 Oxidation of Nickel……………………………………………………20
2-2-2-2 Formation of NiAl2O4…………………………………………………21
CHAPTER 3 EXPERIMENTAL PROCEDURE……………………….24
3-1 The Preparation of Al2O3/Ni Composite Powder by an Ion-Exchange Method...24
3-1-1 The Preparation of Composite Powder…………………………………….24
3-1-2 The Zeta Potential of the Alumina…………………………………………27
3-1-3 X-ray Diffraction Analysis………………………………………………...27
3-1-4 Thermal Analysis…………………………………………………………..29
3-1-5 Quantitative Analysis………………………………………………………29
3-1-6 TEM Observation…………………………………………………………..29
3-2 The Preparation of Al2O3/Ni Composites by Pressureless Sintering in CO…….29
3-2-1 The Preparation of Materials.………………………………………………30
3-2-2 The Preparation of the Test Bars….………………………………………..30
3-2-3 X-ray Diffraction Analysis…………………………………………………30
3-2-4 Measurement of Density…………………………………………………...32
3-2-5 Measurement of Strength…………………………………………………..33
3-2-6 Measurement of Toughness………………………………………………...33
3-2-7 SEM Observation…………………………………………………………..34
3-2-7-1 The Size of Inclusions and Matrix Grains………………………….....34
3-2-7-2 The Interactions between Crack and Inclusions………………………36
3-3 Oxidation of Al2O3/Ni Composites……………………………………………...36
3-3-1 Preparation of Oxidation Specimens……………………………………….36
3-3-2 Measurement of Electrical Resistivity…………………………………..…36
3-3-3 Oxidation………………………………………………………………...…38
3-3-4 X-ray Diffraction Analysis…………………………………………………38
3-3-5 SEM Observation………………………………………………………….38
3-3-5-1 Observation of Surface………………………………………………..40
3-3-5-2 Observation of Oxidation Layer………………………………………40
CHAPTER 4 RESULTS and DISCUSSION……………………………..41
4-1 Preparation of Al2O3/Ni Powder by Ion-Exchange Method…………………….41
4-1-1 The Zeta Potential of the Alumina…………………………………………41
4-1-2 The Preparation of Materials……………………………….………………41
4-1-3 Thermal Analysis…………………………………………………………..46
4-1-4 X-ray Diffraction Analysis…………………………………………………48
4-1-5 Quantitative Analysis……………………………………………………...51
4-1-6 Thermodynamic Analysis………………………………………………….53
4-2 The Preparation of Al2O3/Ni Composites by Pressureless Sintering in CO….…56
4-2-1 Phase Analysis……………………………...………………………………56
4-2-2 Thermodynamic Analysis………………………………...………………..56
4-2-3 Sintering Behavior………………………………………………………….59
4-2-4 The Microstructure Observation…………………………………………...63
4-2-4-1 The Observation of Metallic Nickel…………………………………..63
4-2-4-2 The Observation of Alumina Grains…………………………………..70
4-2-4-3 The Interaction between Crack and Inclusions………………………..81
4-2-5 Mechanical Properties……………………………………………………...81
4-2-5-1 The Flexural Strength of Al2O3/Ni Composites…………………….…81
4-2-5-2 The Fracture Toughness of Al2O3/Ni Composites…………………….84
4-2-6 Critical Size of Second Phase………………………………………………87
4-3 The Oxidation Behavior of Al2O3/Ni Composites………………………………91
4-3-1 Measurement of Electrical Resistivity……………………………………..91
4-3-2 X-ray Diffraction Analysis…………………………………………………91
4-3-3 Analysis of Oxidation Behavior………………………………………..…100
4-3-3-1 Oxidation………………………………………………………….….100
4-3-3-2 Microstructure Observation………………………………………….100
4-3-4 Oxidation Mechanism……………………………………………...…..…114
4-3-5 Activation Energy of Oxidation…………………………………...…..…121
CHAPTER 5 CONCLUSIONS…………………………………………….126
REFERENCES…………………………………………………………….…..129

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