Low Temperature Wasteheat Recovery Based On Bi₂Te₃Thermoelectric Materials

Efficient utilization of energy and recycling of the low-grade energy such as industrial waste heat has great social significance in dealing with energy crisis.Thermoelectric material is a kind of semiconductor material which can realize the direct conversion from heat to electric energy. Waste heat energy can be directly transformed to electric energy by thermoelectric generators which are based on thermoelectric material so that the grade of energy can be improved.The synthesis parameters (such as ball-milling speed, time, and ball material ratio) of Bi2Te3by ball-milling method were researched in this thesis.The thermoelectric thick film was prepared by adding organic components to Bi2Te3powder. The relationship between the preparation parameters and thermoelectric properties of thick film was discussed. The impact of thermoelectric performance by post-treatment such as heat treatment and isostatic cool pressing was investigated. Finally, two types of thermoelectric generators were designed and constructed to realize the applicationon waste heat recovery.As a result, the following conclusions were obtained:1. Higher ball-milling speed and ball material ratio is good for the alloying process of Bi2Te3. After the completely alloying of Bi2Te3, continually increase of the ball millingtime canincrease the grain size, while lead to the reduction of the thermoelectric performance.2. Polystyrene (PS) was dissolved in toluene (TOL), and then the Bi2Te3powder was mixed with the precursor solution. As-obtained paste could be used to produce thermoelectric thick film showing a relative high performance. The increase of the organic components can reduce the conductivity of thick film, but improve the Seebeck coefficient. The optimized process isfound that PS dissolved in TOL as the ratio of2:11, Bi2Te3powder mixed with PS-TOL solution as the ratio of3:2.3. Heat treatment and isostatic cold pressing could improve the thermoelectric performance of thick film. Higher temperature of heat treatment could lead to better performance of thick film. The sample with heat treatment under350°C had the power factor of8μW/m·K2in testing temperature of200℃4. In-plane and cross-plane thermoelectric generators for waste heat recovery were constructed. The cross-plane thermoelectric generator system displayed good power generate capability, but bad heat exchange efficiency. The in-plane thermoelectric generator showed good heat exchange efficiency so that it was suitable for heatexchange demanding occasions...