【作者】 李凯；

【导师】 杨君友；

【作者基本信息】 华中科技大学 ， 纳米科学与技术， 2008， 硕士

【摘要】 热电材料是可以实现热能和电能的直接转换特殊意义的功能材料,近年来随着相关理论特别是纳米技术的发展,热电材料的研究进展迅速。理论分析表明,由于更强的量子禁闭效应,与二维的纳米薄膜材料相比,一维纳米热电材料(纳米棒、纳米管等)可望获得更为优异的热电性能。碲化铋系V-VIA族化合物半导体材料是当前应用最广的热电材料之一,目前对其纳米薄膜超晶格的制备及热电性能的研究已取得重要进展,目前报道的最高ZT值为2.4,而有关碲化铋系一维纳米热电材料的制备及形态控制等问题还没有完全解决。湿化学法应用于热电材料的制备已经有了较多报道,且取得了不错的成果。微波加热与湿化学方法相结合制备纳米热电材料在最近几年开始引起研究人员的重视,本文主要采用微波湿化学方法从事纳米热电材料制备的研究,微波作为特殊的能量源,大大缩短了反应时间,提高了反应效率,由于微波加热十分均匀,能有效消除温度梯度的影响,同时有可能使沉淀相瞬间内萌发形核,获得均匀尺寸的超细粉体。本课题成功制备出了Sb2Te3纳米片和纳米棒及Sb2Se3纳米棒,研究了多种因素对Sb2Te3和Sb2Se3纳米材料合成及形态的影响,对今后的研究工作提供了较好的借鉴意义。通过合理设计实验方案,30min就可以成功制备出单相的Sb2Te3纳米片, pH值是决定能否制备出Sb2Te3单相纳米片的关键因素,提高pH值可以明显缩短获得单相材料所需反应时间。测试结果表明所获得的产物成分均一,不加表面活性剂时为规则的正六边形的纳米片状,当加入表面活性剂十二烷基硫酸钠时出现破碎的枯叶状形态,当加入十二烷基磺酸钠作为表面活性剂时开始出现一维纳米棒,且随表面活性剂量的增加纳米棒的数量不断增加,对可能的反应机理和晶体生长机理进行了分析。选用与前面不同的实验方案成功制备出了纳米Sb2Se3材料,研究表明KBH4在Sb2Se3的制备过程中起到了关键作用,反应60min时可以制备出单相高纯度的Sb2Se3纳米材料,FESEM观察发现其形貌为截面为四边形的棒状结构,尺寸并不均匀。加入十二烷基磺酸钠后,Sb2Se3尺寸明显变得更加均匀,且棒的边缘逐渐变圆滑,有些已经变为圆棒,表面活性剂对粉末形貌的改变起到了关键作用,基本达到了我们预期的目的,我们对可能的反应机理和结晶生长机理进行了分析。更多还原

【Abstract】 Thermoelectric materials, which could be used to achieve the direct transfer between thermal energy and electric energy, are new functional materials with peculiar significance.With the development of nanotechnologies and relevant theories, their thermoelectric performance has been improving rapidly in recent years. Due to their stronger quantum confinement effect, it has been expected that one-dimensional thermoelectric nanomaterials(nanorod, nanotube, nanoline, etc) have more excellent performance than two-dimensional nano films. Currently Bi2Te3-based bulk materials are one of the most widely used thermoelectric materials, and a remarkable progress with ZT=2.4 has been reported in Bi2Te3/Sb2Te3 nano-superlattice system. However, preparation and morphology control to Bi2Te3-based one-dimensional thermoelectric nanomaterials have not been solved. Wet-chemical methods have been tried for preparation bismuth telluride based materials by many researchers, and some successful results have been reported. As a special and effective energy source, microwave heating can greatly reduce the reaction time, and improve the reaction efficiency, furthermore the effect of microwave heating is could eliminate temperature gradient and heat uniformly, so it can be helpful to quick nucleation, and it is easy to get uniform nanomaterials. In this thesis, microwave heating has been combined with wet-chemical method to synthesis bismuth telluride based one-dimensional nanomaterials, and nanorods of both Sb2Te3 and Sb2Se3 compounds have been prepared successfully. Reaction parameters and experimental conditions have been fixed and optimized, and this will be helpful to the future research.Without addition of surfactants, single-phase hexagonal Sb2Te3 nanoflakes have been synthesized within 30 minutes, and it has been found that the pH value is the key factor to the experiments, reaction duration could greatly reduced with increasing the pH value of the reactants. .Adding sodium dodecyl sulfate to the reaction system, the morphology of Sb2Te3 products changes and looks like broken leaves, and then some one-dimension Sb2Te3 nanorods were synthesized while dodecyl sulfonic acid sodium salt was used as surfactants. Increasing the surfactant amount of dodecyl sulfonic acid sodium salt, the fraction of Sb2Te3 nanorods increased as well. A possible reaction mechanism and crystal growth mechanism have been suggested.KBH4 is a key factor to the synthesis of Sb2Se3 nanorod. Without addition of surfactants, single phase Sb2Se3 nanomaterials could be synthesized within 60 minutes, they were inhomogeneous quadrangular nanorods. With addition of dodecyl sulfonic acid sodium salt as surfactants, we found Sb2Se3 products became more homogeneous in size and some changed to round rods. Evidently the surfactants were the key factor which brought this change. A possible reaction mechanism and crystal growth mechanism were proposed.更多还原