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標題: | 金屬玻璃作為Zn4Sb3熱電模組擴散阻障層之可行性 The Feasibility of Metallic Glass as Diffusion Barrier of Zn4Sb3 Thermoelectric Module |
作者: | Chi-Shen Lai 賴其伸 |
指導教授: | 莊東漢 |
關鍵字: | 熱電材料,擴散阻障層,金屬玻璃,介金屬化合物,層狀結構, Thermoelectric material,Diffusion barrier,Metallic glass,Intermetallic compound,Layered structure, |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | Thermoelectric materials play an important role in the issue of green energy. Since many industrial waste heat is present at a temperature between 200-600°C, the development of medium-high-temperature thermoelectric materials becomes more and more important. At present, Zn4Sb3 is quite representative in medium-high-temperature thermoelectric materials, but due to its high activity, Zn can easily penetrate the conventional diffusion barrier layer into the Cu electrode, resulting in the failure of the thermoelectric material, so there is no yet sufficiently durable Zn4Sb3 commercial thermoelectric module. In this study, in order to investigate whether the amorphous structure can effectively enhance the performance of the barrier layer, diffusion couples were prepared by thermocompression bonding using metallic glass Ni-Pd bands and Zn4Sb3 and aging tests were performed. Meanwhile, some amorphours Ni-Pd bands were annealed to crystalline structure and was made into diffusion couples by following the same steps as above, and aging was performed under the same conditions, thereby comparing the difference in the diffusion barrier performance between the amorphous and the crystalline structure.
In most of the sample comparisons, it was found that the thickness of the interface in amorphous diffusion couple was thinner, so it can be inferred that the amorphous structure has a better diffusion barrier performance. Besides, the layered structures that are often found in amorphous diffusion couples are also discussed. It is deduced that the Zn content in the interfacial intermetallic compounds is much larger than that of Ni and Pd, resulting in Ni and Pd atoms being rejected to the original metallic glass matrix. Because the growth rate of the intermetallic compound is much greater than the diffusion rate of Ni and Pd atoms in the metallic glass, the two atoms gradually accumulate at the interface between the intermetallic compound and the metallic glass. Finally, when the cumulative amount reaching an upper limit value, and because the metal glass is too dense at this place, Zn atoms can no longer be arranged in crystalline state therein. Thus, the dense metal glass will remain in the place permanently. After that, Zn atoms will go over the place and go to the next looser metallic glass zone and produce the second layer of intermetallic compound, which in turn generates the observed layered structure. In this study, it was also found that the formation rate of the intermetallic compound was affected by the hot-pressing pressure, and it was inferred that the formation of the intermetallic compound would be accompanied by a violent volume expansion. Therefore, the pressurization can suppress the growth of the intermetallic compound, and simultaneously reduce the difference between the growth rate of the intermetallic compound and the diffusion rate of Ni and Pd atoms, which in turn makes it more difficult to produce a layered structure. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/20112 |
DOI: | 10.6342/NTU201800771 |
全文授權: | 未授權 |
顯示於系所單位: | 材料科學與工程學系 |
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