太陽熱能發電系統是由將太陽光以熱能的形式儲存並在需要電力時將儲存的熱能轉變成電能的裝置。理論上，太陽熱能發電系統可以全天候發電並且提供相當高的發電效率（約40%）。然而，太陽熱能發電系統的熱儲存容量受到了儲存熱能的工作載體的比熱限制，也限制了發電廠的電能產出。

在本研究，錫鋅合金核－氧化矽殼微奈米粒子被合成並進行了一系列的性質分析。由掃描式電子顯微鏡（SEM）與穿透式電子顯微鏡（TEM）觀察，所有的微奈米顆粒皆完整的被氧化矽殼層包覆。藉由退火與X-Ray結晶繞射分析，確認了這些氧化矽殼層保護了內層的金屬顆粒不受氧化。在細心控制錫前驅物與鋅的比例下，藉由X-Ray結晶繞射定量分析確認錫鋅合金顆粒中錫與鋅的比例可以受到控制。利用差示掃描量熱法（DSC）分析，這些微米顆粒呈現了兩個熱吸收峰。其中一個吸收峰座落於錫鋅合金共晶點（200˚C），而另一個吸收峰則隨著錫鋅兩者的比例座落於介於360˚C 至 400˚C處。然而，奈米顆粒的熱性質則與微米顆粒熱性質有所不同。奈米顆粒的熱吸收峰則分別落在錫鋅合金共晶點（200˚C）、錫金屬熔點（230˚C）與鋅金屬熔點（420˚C）處，但是這些吸收峰與純金屬熱吸收峰相比有寬廣化的趨勢。儘管如此，這些合金顆粒在熱循環測試中皆展現良好的熱穩定性。

總結而言，錫鋅合金核－氧化矽殼微奈米粒子展現了可調變的熱性質，並且有潛力被彈性化的使用於在適合的操作溫度區間摻雜到工作流裡改善太陽熱能系統熱儲存性質。

Solar-thermal power generation system is designed for storing sunlight as heat and converting it into electricity when power is needed. Theoretically, it offers electrical power with much higher efficiency (approximately 40%) as compared to, on the average, 20% of its photovoltaic counterparts. The higher efficiency offers a good possibility to overcome the diurnal limitation of solar power. However, the amount of power generation in the solar-thermal system is limited by the amount of thermal energy stored, which is determined by the heat capacity of the working fluid in the solar-thermal power plants.
In this thesis, both SiOx-coated Tin-Zinc-alloy microparticles and nanoparticles are well-coated with silica. The silica shell shows good protection of the interior alloy from oxidation against annealing in air. The results are verified with XRD, SEM, and TEM analyses. Also, the XRD Reference Intensity Ratio (RIR) analyses indicate that the Tin-Zinc composition of the SiOx-coated Tin-Zinc-alloy can be tuned by controlling the relative quantities of the Tin and Zinc precursors. Each DSC measurement of these microparticles contains two peaks resulted from the latent heat. One of them takes place at the eutectic temperature of 200 ˚C and the other falls in the range between 360 ˚C and 400 ˚C depending on the Tin/Zinc ratio. In the case of nanoparticles, the DSC results are different. Instead of two, there are three peaks. One of them is again at the eutectic point at 200 ˚C and the other two are at 230 ˚C and 420 ˚C, which are the melting points of Tin and Zinc, respectively, although the peaks broaden as compared to pure Tin and Zinc. Both micro and nano-particles show good thermal and structural stability when subjected to DSC heat cycle tests.
In summary, SiOx-coated Tin-Zinc-alloy microparticles show tunable thermal properties that can be used as the working fluids in the solar thermal power system for different working temperature ranges. Its temperature tenability adds more flexibility to enhance the heat storage capacities of the solar thermal systems.

Contents I
Abstract III
摘要 IV
Acknowledgement V
Chapter 1 Introduction 1
1.1 Overview of Low-temperature Eutectic Alloy Systems 1
1.2 Synthesis Methods of Binary Alloy Particles 4
1.2.1 Milling Process (Mechanical Alloying) 4
1.2.2 Spray Technique 6
1.3 Chemical Synthesis Techniques 7
1.3.1 Electroless Plating 8
1.3.2 Silica Coating Techniques 9
1.4 Quantitative Analysis Methods and Thermal Properties Measurement 12
1.4.1 Energy-dispersive X-ray Spectroscopy (EDS) 12
1.4.2 X-ray Diffraction Quantitative Analysis by RIR Method 13
1.4.3 Latent Heat and Heat Capacity Measurement 16
1.5 Introduction to Solar Thermal Power Generation Systems 18
1.5.1 The Architecture of the Solar Thermal Power Plant System 20
1.5.2 Molten Salts 22
1.5.3 Enhancement of Molten Salt Heat Capacity by Doping of Phase-transition Materials 23
1.6 Motivation and Research Directions 25
Chapter 2 Experimental Procedures 27
2.1 Chemicals 27
2.2 Synthesis of SnxZn1-x@SiOy Core-shell Microparticles 27
2.1.1 Preparation of SnZn Microparticles 27
2.1.2 Silica Coating of SnZn Microparticles 28
2.3 Synthesis of SnxZn1-x@SiOy Core-shell Nanoparticles 29
2.2.1 Preparation of SnZn Nanoparticles 29
2.2.2 Silica Coating of SnZn Nanoparticles 29
2.4 Characterization 30
2.4.1 SEM and TEM Observation 30
2.4.2 X-ray Diffraction and RIR Quantitative Analysis 30
2.4.3 Latent Heat and Cp Measurements by DSC 31
Chapter 3 Results and Discussion 33
3.1 Composition control of SnxZn1-x microparticles 33
3.1.1 Influence of Amount of Tin Precursor 33
3.1.2 Influence of Reaction Time 36
3.1.3 Influence of pH Values 38
3.2 Coating Quality of SnxZn1-x@SiOy Core-shell Microparticles 40
3.3 Latent Heat and Cp Measurement of SnxZn1-x@SiOy Core-shell Particles 44
3.4 Properties of SnxZn1-x@SiOy Core-shell Particles: Comparison Between Micro- and Nano-size Cases. 46
3.5 Revealing Endothermic Plateau by SnxZn1-x@SiOy Core-shell Particles. 49
3.6 Enhancement of Molten Salt Heat Capacity by Doping Different Compositions of SnxZn1-x@SiOy Core-shell Particles 53
Chapter 4 Summary and Conclusions 55
References 56

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