摘要
本研究利用膠粒製程及乾壓成形法製備添加氧化釔或氧化鎂相穩定劑的氧化鋯材料。燒結體的密度以阿基米德法測定之。研磨加工前、後及經熱處理的試片，其表面的單斜相含量則以XRD測定並以Toraya公式計算。研磨加工及磨耗測試後的表面型態，以掃描式電子顯微鏡(SEM)觀察。同時研磨加工過程中，正向力及切線力則以動力計記錄之。三點、四點抗折強度及破壞韌性分別測定後，再利用磨耗測試機來測定材料性質及測試參數對磨耗的影響。
TZPC及TZPD研磨加工面主要是以塑性變形為主的研磨機制，而PSZD的研磨加工面則以脆性破壞為主及少量的塑性變形的研磨機制。研磨加工過程中除正方晶相相變至單斜晶相，同時也觀察到鐵彈性疇域轉換及菱形晶相的生成。經熱處理後單斜晶相的含量會下降，但I(002)t/I(200)t的比值大於1，即鐵彈性疇域轉換機制為不可逆的相變。
TZPC試片的三點及四點抗折強度分別為785 MPa、韋伯模數11.8及723 MPa、 韋伯模數5.7。對於第二次的三點抗折測試，TZPC試片（取第一次的四點抗折強度測試後較長的樣品）強度由第一次的四點抗折強度641 MPa、韋伯模數8.6降為236 MPa、韋伯模數4.1。此結果顯示強度的下降可能是由於表面單斜晶相的增加或者是測試期間所造成的裂紋成長。
TZPC、TZPD及 PSZD試片以SENB法測得的破壞韌性分別為9.81.0 、7.61.0 及4.71.2 。然而，以壓痕破裂(IF)法所得的值與SENB法測得的破壞韌性值不一致，此結果顯示氧化鋯材料因具有較高的破壞韌性值因此不適合用壓痕破裂法來測定之。
磨耗測試結果顯示出TZPC的磨耗機制以塑性變形為主。此外將所測得的材料性質與磨耗率作圖時，吾人可發現磨耗率與材料性質的關係可由下式表之
其中Rw為磨耗率、Ko為常數、Ｇ為晶粒大小、KIC為破壞韌性、Hv為維式硬度而E為楊氏模數。此外氧化鋁的磨耗機制不同於氧化鋯，主要是以微破裂及晶粒拔出為主的磨耗型態。
關鍵字:膠粒製程、乾壓成形法、研磨、抗折強度、破壞韌性、磨耗

Abstract
In this study, yttria-doped zirconia and magnesia-doped zirconia (Mg-PSZ) powders were used to prepare samples by using colloidal processing/pressure casting and die-pressing methods. The sintered density of Mg-PSZ and Y-TZP sample was measured by Archimedes’ method. The amount of m-phase of as-sintered, ground and annealed samples were determined by quantitative X-Ray diffractometry (XRD) using Toraya’s equation. The morphologies of ground and worn surfaces were examined by scanning electron microscopy (SEM). The normal and tangential forces during surface grinding were recorded by using dynanometer. The 3-point, 4-point flexural strength measurements (including first and second bending), fracture toughness were completed. The wear test was performed by a wear tester to investigate the dependence of material properties and testing parameters on the wear resistance of various materials.
The relative density of TZPC, TZPD, PSZC and PSZD were measured to be 99.8 %, 99.7%, ∼90 % and 99.5%, respectively. The morphologies of ground surface of TZPC and TZPD observed by SEM show a grinding mechanism of major plastic deformation. However, the surface of ground PSZD shows mainly brittle fracture and occasionally plastic deformation. The m-phase content of ground samples increases at the same time. Furthermore, the t-to-m phase transformation, ferroelastic domain switching and r-phase formation were also observed. After hear treatment, the amount of m-phase decreases. But the ratio of I(002)t/I(200)t remains greater than unity, implying the ferroelastic domain switching mechanism is irreversible. During grinding, the normal and tangential forces basically increase with increasing depth of cut from greater speed to lower one.
The 3-point and 4-point flexural strengths of TZPC were 785 MPa with m = 11.8 and 723 MPa with m = 5.7, respectively. For the second 3-point bending strength of the TZPC samples which were obtained from the 4-point bend bars been tested once, the first 4-point flexural strength of the TZPC is 641 MPa with m = 8.6 and reduced to 236 MPa with m = 4.1 for the second 3-point bending test. The results of the second test imply that the reduction of strength is due to either the increment of m-phase on stressing surface or the crack extension during the bending test.
The fracture toughness of TZPC, TZPD, and PSZD measured by single-edge-notched-beam (SENB) method were 9.8±1.3 , 7.6±1.0 and 4.7±1.2 , respectively. However, the value of fracture toughness measured by indentation fracture (IF) method seems to be inconsistent with the value obtained by SENB technique. In other words, the IF method isn’t an appropriate method to measure samples with high toughness.
The wear results show that the morphologies of worn surface of the TZPC exhibit major plastic deformation. The dependence of intrinsic material properties and testing parameters on the wear resistance is very complicated. The results show that the wear rate is proportional to where G is the average grain size, KIC is the fracture toughness, Hv is the Vickers’ hardness and E is the Young’s modulus. Furthermore, the wear mechanism of Al2O3 is different from that of TZPC. For Al2O3, the material removal mechanism is microfracturing plus minor grain pull-out. However, the wear mechanism of TZPC is plastic deformation and wear debris reattachment.
Key words: Y-TZP, Mg-PSZ, colloidal processing, die-pressing, grinding, flexural strength, fracture toughness, wear

Content
Chapter 1 Introduction and Objectives1
Chapter 2 Literature review3
2.1 Zirconia Materials3
2.1.1 Magnesia-Partially Stabilized Zirconia (Mg-PSZ)4
2.1.2 Yttria-Tetragonal Zirconia Polycrystals (Y-TZP)6
2.2 Biomedical Applications of Zirconia8
2.3 Mechanical Property9
2.3.1 Flexural Strength 9
2.3.2 Weibull Statistical Distribution12
2.3.3 Fracture Toughness13
2.4 Wear14
2.4.1 Hardness and Toughness15
2.4.2 Thermal Conductivity16
2.4.3 Microstructure17
Chapter 3 Experimental Procedure21
3.1 Materials21
3.2 Sample Preparation21
3.2.1 Colloidal Dispersion/Casting of Y-TZP and Mg-PSZ21
3.2.2 Die-Pressing of Y-TZP and Mg-PSZ25
3.3 Sintering 28
3.3.1 Mg-PSZ28
3.3.2 Y-TZP28
3.4 Machining 28
3.5 Heat Treatment29
3.6 Property Measurement29
3.6.1 Particle Size Distribution29
3.6.2 Density30
3.6.3 XRD30
3.6.4 Surface Roughness31
3.6.5 SEM Observation31
3.6.6 Measurement of Normal and Tangential Force33
3.6.7 Measurement of Flexural Strength 33
3.6.8 Measurement of Fracture Toughness34
3.6.9 Wear Test35
Chapter 4 Results and Discussion37
4.1 Starting Materials37
4.2 Surface Grinding by Diamond Wheel 37
4.2.1 The Observation of Machined Morphologies 37
4.2.2 Effects of Machining on Phase Transformation44
4.2.3 Measurement of Normal and Tangential Forces during Grinding52
4.3 Mechanical Properties 62
4.3.1 Four-Point Flexural Strength and Weibull Modulus62
4.3.2 Three-Point Flexural Strength and Weibull Statistics74
4.4 Fracture Toughness78
4.4.1 Single-Edge-Notched-Beam (SENB)78
4.4.2 Indentation Fracture (IF)82
4.5 Wear Performances87
4.5.1 The Dependence of Grain Size on Y-TZP87
4.5.2 The Influence of Testing Parameters91
4.5.3 The Wear Comparison between TZP and Al2O3103
4.5.4 Relationship between Material Properties and Testing Parameters108
Chapter 5 Conclusion 112
References115
Appendix 121

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