濕式珠磨法在Bi-Sb-Te熱電材料製備之應用研究

Characterization of Bi-Sb-Te powders prepared by wet bead milling

李祖霆(Tzu-Ting Lee)

指導教授 ： 廖建能

國立清華大學/工學院/材料科學工程學系/碩士(2013年)

https://doi.org/10.6843/NTHU.2013.00119

摘要

熱電材料一直以來被視為具有潛力的能源轉換材料之一，此材料可將電能及熱能進行直接轉換。其便利性及穩定性為熱電材料應用重點。近年研究發現奈米結構熱電材料具備優良的熱電性質。而碲化鉍為室溫下應用範圍最廣之熱電材料，因此本研究嘗試利用濕式珠磨製程製作Bi-Sb-Te化合物奈米粉末並壓錠塊材，探討其熱電傳輸性質。
本實驗Bi-Sb-Te奈米結構塊材製備方式為先利用行星式球磨法將Bi-Sb-Te合金鑄錠初磨至微米等級以下，再以(JBM-B035)珠磨機成功粉碎至奈米粒徑，再以冷壓法壓錠試片，並對此試片作分析了解。此研究重心為珠磨法對於熱電材料的影響及其可行性。研究結果顯示，濕式珠磨法能夠對Bi-Sb-Te合金粉末施以高能量衝擊，使粉末粒徑縮小至奈米等級，但亦導致粉末結晶結構劇烈破壞同時使奈米合金粉末氧化。微結構觀察顯示氧化非晶態層結構，散佈在Bi-Sb-Te粉末中。Bi-Sb-Te材料氧化以及其晶體結構破壞影響冶金性質，使試片不易壓錠成形。因此添加氫還原製程，目的是將合金材料氧化部分去除並恢復材料冶金性質。此製程可使粉體還原並再生長形成Bi-Sb-Te合金粉末，結果顯示粉末粒徑大小快速增長，晶體傾向片狀結構的生長，使材料粉體再生長時具有(00l)晶面優選方向。晶體的成長與基面優取方向導致電導性質與熱導性質的增強，進而改變材料熱電性質。

關鍵字

濕式珠磨 ； 熱電材料 ； 塊材 ； 奈米粉末 ； 冷壓

並列摘要

Thermoelectric material which converts electrical energy into thermal energy directly, and vice versa, has been regarded as a potential energy conversion material. Recent studies have found nanostructured thermoelectric materials can create better thermoelectric properties and lead to better thermoelectric conversion efficiency. In this study, Bi-Sb-Te compounds nano-powders were prepared by wet bead milling process and pressed into a sample. The effects of processing conditions on thermoelectric properties of cold-pressed Bi-Sb-Te are investigated.
In this study, Bi-Sb-Te powders of micro-meter size were first prepared by a planetary ball milling, and then refined into nano-size particles by wet beads milling method. Finally, these powders were pressed into a bulk at room temperature. We found some problems occurring during the wet-milling process. Bi-Sb-Te alloy powders prepared by wet bead milling are subjected to serious damage of crystal structure and oxidation. The oxidation affects the metallurgical properties of the Bi-Sb-Te material and crystal structure, results in specimen's compactness. Here, we added an additional hydrogen reduction process to recover the ground B-Sb-Te powders by removing the oxidized part and restoring the thermoelectric properties of the pressed Bi-Sb-Te compound. The results show that the Bi-Sb-Te powders have a (00l) preferred orientation and the Bi2Te3 crystal reveals laminar structure. The pressed Bi-Sb-Te with (00l) preferred orientation has enhanced electricity conductivity and thermal conductivity as well as thermoelectric figure-of-merit.

並列關鍵字

wet bead milling ； thermoelectric ； bulk material ； nanopowder ； cold pressed

參考文獻

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