指導教授：段維新臺灣大學：材料科學與工程學研究所連增文Lian, Tseng-WenTseng-WenLian2014-11-262018-06-282014-11-262018-06-282014http://ntur.lib.ntu.edu.tw//handle/246246/262044以3 mol%氧化釔安定之氧化鋯(3YSZ)具有優異的機械性質，如高強度及高韌性等。近年來在3YSZ中加入20wt%的氧化鋁(Al2O3)粉也因為其具有優秀的強度及熱穩定性而被廣泛應用。本研究將微量(0-2 mol%)的氧化鈮(Nb2O5)加到3YSZ及3YSZ/20wt%Al2O3中。試樣在空氣氣氛中進行燒結，持溫時間為一小時。本研究探討了添加氧化鈮對於相穩定性、微結構、機械性質、以及熱傳導性質的影響。 結果顯示當添加0.5 mol %氧化鈮時，3YSZ及3YSZ/20wt%Al2O3的破壞韌性將大幅度增加。當氧化鈮含量增加時，在試樣中的正方相氧化鋯將變得不穩定。不穩定的正方相氧化鋯易發生相變化，而伴隨的相變化增韌機制，使此兩氧化鋯系統的破壞韌性的提升。其他機械性質如強度以及硬度在本系統中並沒有隨著微量氧化鈮的添加而有明顯的變化。 3YSZ/20wt%Al2O3/Nb2O5相較於3YSZ/Nb2O5表現出較高的強度和韌性。強度以及韌性的增加源於3YSZ/20wt%Al2O3中的殘餘應力。The 3 mol% Y2O3-stabilized zirconia (3YSZ) exhibits excellent mechanical properties such as high strength and high fracture toughness. Recently, 3YSZ/20wt%Al2O3 powder has also been widely used for its excellent strength and thermal stability. In the present study, a small amount (0-2 mol%) of niobium oxide (Nb2O5) was added into 3YSZ and 3YSZ/20wt%Al2O3 systems. The specimens were sintered at 1600°C in air for 1 hour. The effect of Nb2O5 addition on the phase stability, microstructure, mechanical properties and thermal conductivity was then investigated. The results indicate that the fracture toughness is increased significantly after the addition of 0.5 mol % Nb2O5 both in the 3YSZ and in 3YSZ/20wt%Al2O3 systems. The tetragonal ZrO2 phase in the composites becomes unstable as the Nb2O5 content is high. The instability of tetragonal ZrO2 promotes its transformability, it results in the phase transformation from tetragonal phase to monoclinic phase. The toughening mechanism induces the increase of fracture toughness in the zirconia systems. Other mechanical properties such as strength and hardness remain the same after the addition of a small amount of Nb2O5. The 3YSZ/20wt%Al2O3/Nb2O5 specimens exhibit higher flexural strength and higher fracture toughness comparing to those of the 3YSZ/Nb2O5 specimens. The increase of flexural strength and fracture toughness may be related to the presence of residual stress in the ZrO2-Al2O3 systems.Chapter 1 Introduction 1 Chapter 2 Literature Survey 2 2-1 ZrO2 System 2 2-1-1 Phases of Zirconia 2 2-1-2 Yttria-Stabilized Zirconia (YSZ) System 2 2-1-3 Grain Growth of Zirconia 3 2-1-4 Transformation Toughening of Zirconia 4 2-1-5 Strength of YSZ 5 2-1-6 Fracture toughness of YSZ 6 2-2 3YSZ/20wt%Al2O3 System 13 2-2-1 Strength of 3YSZ/20wt%Al2O3 13 2-2-2 Fracture toughness of 3YSZ/20wt%Al2O3 14 2-3 3YSZ/Nb2O5 System 16 2-3-1 Solid Solution and Phase Stability 16 2-3-2 Density and Grain Size 17 2-3-3 Strength and Fracture Toughness of 3YSZ/Nb2O5 18 2-3-4 Ionic Conductivity of 3YSZ/Nb2O5 18 Chapter 3 Experimental Procedures 23 3-1 3YSZ/Nb2O5 23 3-1-1 Materials 23 3-1-2 Powder Mixture 23 3-1-3 Sintering 23 3-1-4 Characterization of Sintered Specimens 24 3-1-4-1 Phase Identification 24 3-1-4-2 Quantitative Analysis 24 3-1-4-3 Density Measurement 25 3-1-4-4 Microstructure Observation 26 3-1-5 Mechanical Properties 27 3-1-5-1 Young''s Modulus 27 3-1-5-2 Flexural Strength 27 3-1-5-3 Fracture Toughness and Hardness 28 3-1-6 Thermal Conductivity 29 3-2 3YSZ/20wt%Al2O3/ Nb2O5 29 3-2-1 Materials 29 3-2-2 Powder Mixture 30 3-2-3 Sintering 30 3-2-4 Characterization of Sintered Specimens 30 3-2-5 Mechanical Properties 31 3-2-6 Thermal Conductivity 31 Chapter 4 Results 33 4-1 3YSZ/Nb2O5 33 4-1-1 Phase Identification 33 4-1-2 Densification 34 4-1-3 Microstructure Observation 35 4-1-4 Mechanical Properties 36 4-1-5 Thermal Conductivity 38 4-2 3YSZ/20wt%Al2O3/Nb2O5 48 4-2-1 Phase Identification 48 4-2-2 Densification 50 4-2-3 Microstructure Observation 51 4-2-4 Mechanical Properties 52 4-2-5 Thermal Conductivity 55 Chapter 5 Discussion 69 5-1 3YSZ/Nb2O5 69 5-1-1 Phase Identification 69 5-1-2 Densification 70 5-1-3 Microstructure Observation 71 5-1-4 Mechanical Properties 71 5-1-5 Thermal Conductivity 73 5-2 3YSZ/20wt%Al2O3/Nb2O5 79 5-2-1 Phase Identification 79 5-2-2 Densification 79 5-2-3 Microstructure Observation 80 5-2-4 Mechanical Properties 81 5-2-5 Thermal Conductivity 82 5-3 3YSZ/Nb2O5 vs. 3YSZ/20wt%Al2O3/Nb2O5 86 5-4 Nb2O5 vs. NiO 89 5-5 General Discussion 92 Chapter 6 Conclusions 94 Reference 9510134049 bytesapplication/pdf論文公開時間：2014/08/21論文使用權限：同意有償授權(權利金給回饋學校)氧化鈮氧化釔安定氧化鋯正方相氧化鋯韌化機制破壞韌性強度硬度thesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/262044/1/ntu-103-R00527005-1.pdf