【作者】 李娜；

【导师】 陈永胜；

【作者基本信息】 南开大学 ， 高分子化学与物理， 2013， 博士

【摘要】 碳纳米管,可以看作由单层石墨碳卷曲而形成的一维中空圆柱型管状结构。而基于石墨层数的不同可以将碳纳米管分为单壁碳纳米管和多壁碳纳米管。碳纳米管在电子学、力学、热学、光学,化学,电化学等多个方面都具有优异的性质,这也使得它们在多个领域拥有具有巨大的应用前景。然而,目前碳纳米管的这些优异性质尚未被广泛有效地开发利用,这是因为许多尚未解决的难题的制约。本文针对碳纳米管在实际应用中的两个难题,分别是单壁碳纳米管优异的电子学性能的应用受其金属型与半导体型混杂的生长方式的制约；以及在碳纳米管作为人工肌肉的应用中,与这个领域其它当代的材料技术一样存在的诸如响应速度不高,应变或应力过低,循环寿命不够,驱动滞后响应,依赖于电解质溶液以及使用温度区间狭窄等问题。我们设计并研究了以下课题,期望能够解决这些难题,并帮助推动碳纳米管的实际应用：1.二氧化碳辅助电弧法选择性生成半导体型富集的单壁碳纳米管。实验结果表明,在电弧放电反应气氛中引入一定量二氧化碳,可以对金属型以及小管径单壁碳纳米管进行原位刻蚀,获得管径大于1.5nm,相对含量为90%的半导体型结构且几乎不含无定型碳杂质的单壁碳纳米管产物。研究中对比发现,使用半导体型富集的单壁碳纳米管作为助催化剂,相对无选择性单壁碳纳米管,可以更大程度地提高二氧化钛光催化分解水制氢反应的效率。2.碳纳米管纺线及其与聚合物的复合材料作为电、光、化学响应的转动和收缩类型的超强人工肌肉。目前只有很少数种类的人工肌肉技术被真正商业化。其主要原因是由于现有的人工肌肉还存在很多问题,具体包括响应速度慢、应力应变低、循环寿命小、依赖于电解液以及能量转换效率低等等。我们的工作中设计制备了一种以碳纳米管纺线为主体,聚合物为客体的复合材料,实现了不需要电解液,并能获得快速响应、大应力、大应变、高功率的转动和收缩类型的人工肌肉。在超过百万次以上循环工作后,转动和收缩类型的人工肌肉的工作效果都没有降低,并且可以达到平均速度为每分钟11,500转的转动效果；以及当响应速度为每分钟1200个循环时,收缩应变为3%的收缩效果。这种复合物人工肌肉的转动或收缩运动可以分别由电、光、热或者化学吸附和脱附引发所引发的客体材料的体积变化来驱动。在这个工作中,我们分别展示了由这种复合材料制成的转动机、收缩肌肉以及可以将感应过程中的能量变化转变为机械能变化的传感器。更多还原

【Abstract】 Carbon nanotubes can be seen as one-dimensional, hollow, cylindrical structures formed by coaxial layers of graphene. The layers are called walls. Based on the number of walls, carbon nanotubes can be divided into single-walled carbon nanotubes and multi-walled carbon nanotubes. Carbon nanotubes have excellent electronic, mechanical, thermal, optical, chemical and electrochemical properties, which enable great potential applications in many related areas. However, there are still some problems that limit their practical application. One of the main problems for single-walled carbon nanotubes is the mixed growth of semiconducting and metallic species, which greatly inhibits their use as high performance electronics. Another specific issue is in the field of artificial muscles. Carbon nanotubes have numerous fundamentally different uses in artificial muscles, however, together with other current techniques in this area, there exist a lot of major limitations, including slow response, low work capacity, short cycle life, huge hysteresis, a reliance on electrolytes, and/or a narrow temperature range for operation. In order to solve these above mentioned problems and help promote the practical application of carbon nanotubes, we have explored the following studies:1. Synthesis of semiconducting SWNTs by arc discharge and their enhancement of water splitting performance with TiO2photocatalyst. A feasible and scalable CO2-assisted arc discharge method was developed to directly synthesize single-walled carbon nanotubes (SWNTs) with largely semiconducting species. Not only was electronic-type selectivity achieved on a large scale, with a semiconducting SWNT (s-SWNT) content of>90%, but also diameter selectivity was obtained, with a majority having diameters of>1.5nm. The photo-catalytic water splitting performance of these SWNTs with different ratios of s-SWNTs to metallic single-walled carbon nanotubes (m-SWNTs) was examined. The results show that, compared with m-SWNTs, s-SWNTs demonstrate a much better photocatalytic effect when used together with the common photo-catalyst TiO2. 2. Electrically, chemically, and photonically powered torsional and tensile actuation of hybrid carbon nanotube yarn muscles. Artificial muscles are of practical interest, but few types have been commercially exploited. Typical problems include slow response, low strain and force generation, short cycle life, use of electrolytes, and low energy efficiency. We have designed guest-filled, twist-spun carbon nanotube yarns as electrolyte-free muscles that provide fast, high-force, large-stroke torsional and tensile actuation. More than a million torsional and tensile actuation cycles are demonstrated, wherein a muscle spins a rotor at an average11,500revolutions/minute or delivers3%tensile contraction at1200cycles/minute. Electrical, chemical, or photonic excitation of hybrid yarns changes guest dimensions and generates torsional rotation and contraction of the yarn host. Demonstrations include torsional motors, contractile muscles, and sensors that capture the energy of the sensing process to mechanically actuate.更多还原