학위논문 (석사)-- 서울대학교 대학원 : 재료공학부, 2016. 2. 남기태.Calcium phosphate compounds are used as a bone implant material for the treatment of bond related disease or injury. Among many calcium phosphate compounds, hydroxyapatite (HAP, Ca10(PO4)6(OH)2) and β-tricalcium phosphate (β-TCP, Ca3(PO4)2) are the most widely used. Although the major components of natural bone are calcium and phosphate, there are many other ions in the bone such as carbonate, sodium, and kalium. Therefore, many studies about ion substitution in HAP were reported. Especially, the carbonate substituted hydroxyapatite is of great interest because of its composition similarity with natural bone and potential to enhance bioactivity of bone grafts. There are many carbonate hydroxyapatite synthesis methods, but most of them use carbon containing chemical for the source of substituted carbonate during the synthesis.
In this research, nano-carbonate hydroxyapatite (CHA) was successfully synthesized through wet precipitation method in aqueous solution. By creating superoxide anion radical in the system, atmospheric CO2 was captured and used as a source of carbonate groups in CHA. CHA formation was confirmed using XRD and FT-IR analysis, and comparison study between synthesized CHA and HAP was carried out. The gas chromatography result showed that our CHA synthesis system absorbed large amount of CO2 in the air efficiently. After that, we observed phase transformation occurred during the CHA synthesis. The result showed that dicalcium phosphate dehydrate (DCPD) was intermediate phase of CHA. Lastly, we succeeded in controlling substituted CO3 amount in CHA by controlling used H2O2 amount. As a result, we successfully synthesized CHA with bone similar composition.
This research has two major impacts. First of all, this synthesis method proposes a new way to mineralize large amount of atmospheric CO2 and use the mineralized form of CO2 as the carbon source of CHA. Second, synthesized CHA can be used as bone implant material because of its chemical composition similarity to natural bone. Consequently, our CHA synthesis system presents the innovative method for synthesizing bone implant material while capturing atmospheric CO2.Chapter 1. INTRODUCTION 1
1.1 Introduction of biominerals and calcium phosphate compounds as bond implant material 1
1.1.1 Chemical composition of human bone 1
1.1.2 Requirements for bone implant material 2
1.1.3 Synthetic calcium phosphate compounds as bone implant material: hydroxyapatite and β-tricalcium phosphate 3
1.2 Carbonate hydroxyapatite 7
1.2.1 Types of carbonate hydroxyapatite 7
1.2.2 Carbonate hydroxyapatite as bone implant material 11
1.2.3 Synthesis methods of carbonate hydroxyapatite 15
1.3 Carbon capture and storage (CCS) 16
1.3.1 Atmospheric CO2 concentration and current status 16
1.3.2 Carbon capture & storage methods 19
1.3.3 Air capture 22
1.4 Carbonation of metal hydroxide sorbents 24
1.4.1 Alkali/Alkali earth metal hydroxide sorbents 24
1.4.2 Superoxide effect 28
1.5 Research scope and design 30
Chapter 2. MATERIALS AND EXPERIMENTS 32
2.1 Sample preparation of carbonate hydroxyapatite 32
2.1.1 Materials 32
2.1.2 Synthesis of carbonate hydroxyapatite 32
2.1.3 Amount modification of substituted carbonate in carbonate hydroxyapatite 35
2.2 Characterization 37
2.2.1 Powder X-ray diffraction (XRD) 37
2.2.2 Field emission scanning electron microscopy (FESEM) 37
2.2.3 Fourier transform infrared spectroscopy (FT-IR) 38
2.2.4 Element analyzer 38
2.3 Carbonation confirmation 39
2.3.1 Electron paramagnetic resonance (EPR) 39
2.3.2 Gas chromatography (GC) 41
2.4 Stability of synthesized carbonate hydroxyapatite 41
2.4.1 Solubility test 41
Chapter 3. RESULT AND DISCUSSION 43
3.1 Material characterization 43
3.1.1 Characterization of carbonate hydroxyapatite 43
3.1.1.1 XRD and SEM studies 43
3.1.1.2 FT-IR studies 49
3.1.2 Solubility of carbonate hydroxyapatite 52
3.2 CO2 absorption during the process 55
3.2.1 CO2 absorption from the air 55
3.2.2 Confirmation of radical formation 58
3.3 Phase transformation during carbonate hydroxyapatite formation 61
3.3.1 Phase transformation during the synthesis 61
3.4 CO3 substituted amount control 70
3.4.1 H2O2 amount effect 70
Chapter 4. CONCLUSION 75
References 77
초 록 86Maste
