本研究旨在生物活性玻璃之合成及經回火或去玻璃化後之微結構與彈性變化之分析。我們合成兩種生物活性玻璃,一富含磷(P)之45S5及較少磷之55S4.3。在經過回火後,所製備的生物活性玻璃為透明狀,其中55S4.3為無色而45S5呈現淡粉紅色。經DTA分析後,發現45S5與55S4.3分別在620oC與680oC開始結晶。在715oC去玻璃化後,兩種生物活性玻璃皆變乳白,且其不透明度隨著熱處理的時間延長而增加。45S5的結晶相為由Na2CaSiO4所衍生之Na2Ca2Si3O9或Na4CaSi3O9。藉由XRD及偏光顯微鏡的觀察,我們推論此結晶為立方體結構,空間族群為P213 (198)且晶格參數a=7.5054Å。較少磷的55S4.3因其結晶速率較慢,故本文並未詳細探討。但因去玻璃化的45S5與55S4.3在Raman光譜中有類似的結果,我們推論兩者結晶有相似的結構。
Raman光譜指出,經回火的45S5主要的譜帶為Q2及Q3且Q3/ Q2隨著在715oC熱處理的時間增加而變小。至於回火後的55S4.3,主要譜帶為Q3,而其強度較在45S5中要高。隨著Na+/Si4+比例增加,在946(或947)cm-1譜帶增加而接近1100 cm-1的譜帶則減弱。經比較去玻璃化的45S5與55S4.3的Raman光譜,我們發現在兩種玻璃中的結晶有一共同的結構單元,SiO32-(Q2)。藉由布里洛散射所量測的結果,我們發現去玻璃化的45S5彈性常數比未去玻璃化(即僅經回火處理)的45S5與55S4.3高。而此生物活性玻璃之彈性又比氫氧基磷灰石及氟基磷灰石小。

The objective of this research is to synthesize and characterize microstructures and some elastic properties of bioactive glasses subject to relaxation and/or devitrification treatments. We synthesize two kinds of bioglasses, i.e. P-richer 45S5 and P-poorer 55S4.3. After tempering, the as-prepared bioactive glasses are transparent, 55S4.3 being colorless while 45S5 pale pink in color. The thermal events in DTA analysis indicated that the crystallization of 45S5 and 55S4.3 starts at 620oC and 680oC, respectively. The two bioactive glasses became ivory upon heating at 715oC, and the degree of being opaque increases with dwelling time.
The crystalline phase for 45S5 is Na2CaSiO4 -derived Na2Ca2Si3O9 or Na4CaSi3O9. By XRD traces and polarizing optical micrographs, we conclude that the crystal is based on simple cubic structure with a=7.5054Å and space group P213 (198). Due to poor crystallization rate, the crystal in P-poor 55S4.3 glass was not investigated in detail. However, according to the similarity of Raman spectra for devitrified 45S5 and 55S4.3, we suggest that the crystal is similar for the two devitrified glasses.
Raman spectra indicated that the relaxed 45S5 has predominant Q2 and Q3 species and the Q3/Q2 ratio decreases with firing time at 715oC. As for relaxed 55S4.3, the major structural unit is Q3, and the intensity of Q3 is higher for 55S4.3 than 45S5. As the Na+/Si4+ ratio increases, the intensity of 946 (or 947) cm-1 increases while bands near 1100 cm-1 decrease. Based on the Raman spectra of devitrified 45S5 and 55S4.3, the crystals in the two glasses have a common structural unit of SiO32- (Q2).
The elasticity measurement by Brillouin scattering indicated that the moduli for devitrified glass 45S5 are greater than undevitrified 45S5 and 55S4.3 glass. The elasticity of the present bioactive glasses is lower than hydroxyapatite and fluorapatite.

Contents
Abstract I
List of Tables III
List of Figures IV
Chapter 1. Introduction 1
Chapter 2. Literature Review 4
2-1 Hydroxyapatite 5
2-2 Crystallization Behavior of Some Bioactive Glass-ceramics 6
2-3 Bioactive Glass Used in This Study 6
2-4 Raman Spectra Analysis 8
2-5 Elastic modulus 10
Chapter 3. Experimental 11
3-1 Powder batches of glasses 11
3-2 Preparation of Glasses 11
3-3 Differential thermal analysis 12
3-4 Devitrification treatment 12
3-5 X-ray diffraction 13
3-6 Raman spectroscopy 13
3-7 Polarizing optical microscopy and electron microscopy 13
3-8 Brillouin scattering measurements 14
Chapter 4. Results 16
4-1 DTA 16
4-2 Devitrification 16
4-2-1 X-Ray diffraction 16
4-2-2 Raman spectra 17
4-2-3 Polarizing optical microscopy 19
4-2-4 SEM and TEM 20
4-2-5 Brillouin scattering 21
Chapter 5. Discussion 22
5-1 Structures of the bioactive glasses 22
5-2 Crystallization behavior 25
5-3 Elasticity change 26
Chapter 6. Conclusion 28
References 29
Appendix 63

List of Tables

Table 1. Requirements for Biomaterials 34
Table 2. Main composition of apatite in dentin and bone 34
Table 3. Raman frequencies of the stretch vibrations of silicate anionic structural units 35
Table 4. Composition of 45S5 35
Table 5. Composition of 55S4.3 36
Table 6. Firing conditions for bioactive glasses 36
Table 7. Devitrification treatment time for bioactive glasses at 715oC 37
Table 8. DTA data of 45S5 and 55S4.3 at 10oC/min 37
Table 9. XRD analysis of 45S5 devitrified at 715oC for 45min 38
Table 10. Raman bands of bioactive glasses devitrified at 715oC 39
Table 11. EDX of Fig. 15 (45S5 heat-treated for 15 min) 39
Table 12. Elasticity of bioactive glasses 39



List of Figures

Fig. 1. System Na2O-CaO-SiO2 (mol %) 40
Fig. 2. System Na2O-SiO2-P2O5 (mol %) 40
Fig. 3. An Ashby diagram with the modulus of sintered hydroxylapatite, porous hydroxylapatite and polymer-apatite composites 41
Fig. 4. DSC traces of the as-prepared bioactive glasses 42
Fig. 5. DTA traces of the as-prepared bioactive glasses 43
Fig. 6. XRD pattern (CuKα)of the as-prepared 45S5 showing broad diffraction maxima with 2θ at 32o 44
Fig. 7. XRD pattern (CuKα)of the as-prepared 55S4.3 showing broad diffraction maxima with 2θat 29.8o . 44
Fig. 8. XRD patterns (CuKα) for 45S5 treated at 715oC for (a) 15 minutes, (b) 30 minutes, (c) 45 minutes, and (d) 1 h. 45
Fig. 9. XRD patterns (CuKa) for 55S4.3 treated at 715oC for (a) 30minutes, (b) 45 minutes, (c) 1 hr, and (d) 1.5 hr. 47
Fig. 10. Raman spectrum of (a) 45S5 glass (tempered at 535oC for 1 hr) (b) 55S4.3 glass (tempered at 575oC for 1 hr). 49
Fig. 11. Raman spectra of partially devitrified 45S5 (with crystals) after heat-treatment at 715oC for (a) 15minutes, (b) 30minutes, (c) 45minutes, and (d) 1hr. 50
Fig. 12. Raman spectra of partially devitrified 55S4.3 (with small clusters and/ or crystalline particles) after heat-treatment at 715oC for (a) 30min, (b) 45min, (c) 1 hr, and (d) 1.5 hr. 52
Fig. 13. Polarizing optical micrographs (open and crossed nicol) of 45S5. 54
Fig. 14. Polarizing optical micrographs of 55S4.3 56
Fig. 15. SEM images (SEI) of 45S5 after devitrification treatment at 715oC for 15min. 58
Fig. 16. TEM image of 45S5 after aging at 715oC for 1 hr 59
Fig. 17. TEM image of 45S5 after aging at 715oC for 1 hr 60
Fig. 18 Diagram of Brillouin scattering 62
Appendix I Sketch of NBO/Si ratio 63
Appendix II Diagram of Brillouin scattering 64
Appendix III Pictures of 45S5 and 55S4.3 65
Appendix IV Sketch of space group P213 (198), JCPDS file 24-1069 67
Appendix V Spectra of Fig. 15 69

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