| Summary: | 碩士 === 國立中央大學 === 機械工程研究所 === 100 === The problems of energy shortage and environment pollution are going seriously. It is important to find alternative energy source project. Thermoelectric materials have thermoelectric properties that can transport heat energy to electric energy without external work. Semiconductor thermoelectric materials power generator is working under Seebeck thermoelectric Law. By establishment of the temperature difference across the materials circuit, we can get voltage across power generator. The advantage of this technology is small volume, quiet, no vibration, no pollution and low maintenance cost. Thermoelectric materials properties can be defined as the figure of merit. The figure of merit is defined as ZT = α2σ/κ, where α is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity and T is the temperature in Kelvin. Therefore, a good material should possess high electrical conductivity, large Seebeck coefficient and low thermal conductivity to retain the heat at the junction and to reduce the heat transfer losses. Most of thermoelectric materials’ ZT value are lower than 1. They do not have potential for commercial application.
The purpose of this program will prepare high performance medium-temperature thermoelectric alloy powder, Zn4Sb3 with nano-structure by means of rapidly-quenched melt-spinning (MS) technique. Then, these rapidly quenched nano-structured alloy ribbons will be ball milled into fine powder and pressed by hot pressing under vacuum to form the bulk samples. The final product fabricated via this new process is expected to increase its power factor ( α2σ ) and reduce thermal conductivity in comparison with the conventional process. In addition, the relationship between the microstructure (grain size) of alloy and its process condition as well as the effect of microstructure on the thermoelectric performance will be investigated.
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