本文采用两步法制备Bi_2Te_3/碳纳米管复合材料.用硝酸溶液对碳纳米管进行超声纯化处理并使其表面活化;采用乙二醇作为溶剂与还原剂、Bi(NO_3)_3和Na_2TeO_3作为前驱体、乙二胺四乙酸(EDTA)作为表面活性剂,以NaOH调节溶液pH值,在200W功率下超声处理90min,得到均匀包覆于碳纳米管表面的中间产物为Bi_xTe_yO_x.用NaBH_4还原以上中间产物得到最终产物.用XRD、TEM、SEM等手段对反应中间及最终产物的形貌与微结构进行了表征.结果表明,Bi_2Te_3纳米颗粒分散连接于碳纳米管表面,所得Bi_2Te_3产物晶粒尺寸为12nm左右.使用表面活性剂和控制反应速率,使Bi_2Te_3非均匀形核被认为是将Bi_2Te_3包覆在碳纳米管表面的关键因素.
A two-step method to prepare Bi_2Te_3/carbon nanotubes (Bi_2Te_3/CNTs) composites was introduced to improve thermoelectric properties of Bi_2Te_3. Firstly carbon nanotubes were purified and modified in nitric acid under ultrasonic waves, glycol was then used as the solvent and reductant, Bi(NO_3)_3 and Na_2TeO_3 as reaction precursors, EDTA as the surfactant, and NaOH was used to adjust the pH value. After 90 minutes synthesis under 200 Watt ultrasonic, intermediate Bi_xTe_yO_x coating on the surfaces of nanotubes was produced. Secondly, this intermediate was reduced by NaBH4 and Bi_2Te_3/CNTs composite was synthesized. The intermediate and final products were characterized by XRD, TEM and SEM. Experimental results showed that the Bi_2 Te_3 nano-particles were densely and uniformly coated on modified surfaces of carbon nanotubes. The heterogeneous nucleation on the carbon nanotubes, induced by both the use of surfactant and the control of the reaction rate, is considered to play an important role in synthesizing Bi_2Te_3/CNTs composites.
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