【作者】 雷佑安；

【导师】 熊传溪；

【作者基本信息】 武汉理工大学 ， 材料学， 2008， 博士

【摘要】 碳纳米管类流体是一类在无溶剂条件下具有类似液体能够流动的新型纳米流体。本文通过多壁碳纳米管的酸氧化和表面有机接枝方法制备了新型多壁碳纳米管类流体,并系统研究了它们的特殊流变性和组装结构。研究发现:均匀设计法是一种高效的筛选碳纳米管酸氧化条件和进一步制备特定流变性碳纳米管类流体的方法。DC5700接枝氧化碳纳米管（DC5700-g-MCNTs）的优化反应条件为:V（碳管酸液）:V（甲醇）:V（40wt%DC5700/甲醇溶液）=1:1:0.2,60℃/2h。其中,DC5700加入碳管/浓酸溶液中能迅速产生絮凝,该现象能广泛地应用于包括CNTs,SiO₂,TiO₂以及Fe₂O₃等在内的诸多纳米粒子的液相分离和提取。因而是一类全新的高效、环保的纳米分离方法,可望在降低纳米材料对人体和环境的危害方面发挥重要作用。研究证实该絮凝方法主要基于化学和物理（范德华力和静电引力）的作用机制。实验中我们观察到了氧化碳纳米管在DC5700功能化的玻片表面的特殊组装结构:1～5μm的碳纳米管岛和宽～1μm长5～15μm的碳纳米管棒,该现象为纳米粒子的组装结构提供了新的途径。DC5700-g-MCNTs进一步和NPES反应能得到新型纳米类流体MCNTs-IL。流变性能研究证实了它在无溶剂条件下具有类液体行为。该方法有望实现难于加工的“固体”碳纳米管象普通高分子、胶体甚至液体一样进行加工。产品室温下为黑色无定形蜡状物,热稳定性较好（失重率10%时温度高达311℃）。电镜观察表明它具有垂直于碳纳米管表面的双离子层结构,厚度约为6.5nm。PEG同样能接枝到碳纳米管表面制得准一维结构的PEG-MCNTs纳米类流体。该类流体表现出不同于以往文献报道的各种0维纳米粒子类流体的特殊流变行为。即较长的PEG-MCNTs粘度大但在20-80℃范围内呈现粘性响应,但粘度较小的短PEG-MCNTs表现为固态弹性流变行为,并在56.7℃实现固-液转变。通过稳态剪切模型的研究,我们发现了碳纳米管表面功能化密度、长径比以及体积分数与碳纳米管类流体宏观流变性的定量关系式,即1/J·x=K·exp（-Ea/RT）（或a/x=K’·exp（-Ea/RT））。该关系式为特定流变行为碳纳米管类流体的制备提供了理论基础,并可以通过酸氧化碳纳米管的简单控制来实现。制得的新型特定碳纳米管类流体可望在新型传感器、纳米器件以及纳米复合材料等众多领域有重大应用前景。更多还原

【Abstract】 In this work,novel multi-walled carbon nanotube fuids（MCNTFs）with unique rheologic behavior and assembley structures were preparaed through acids oxidation and chemical grafting.Uniform design was found to be very helpful in the production of oxidized carbon nanotubes（o-CNTs）and CNTFs.In other words,our method can produced o-CNTs with specific lengthes and functionalizations,which can pave the way for CNTFs with unique rheological responses.The optimized reaction condition for chemical grafting of DC5700 onto o-MCNTs to give DC5700-g-MCNTs are:V （MCNTs/acids）:V（methol）:V（40wt%DC5700/methol）=1:1:0.2,60℃/2h。Outstandingly,flocculational DC5700-g-MCNTs can be readily observed,which can be exploited for a practical protocol to protect us through rapid clearing versatile nanoparticles,including carbon nanotubes,SiO₂,TiO₂ and Fe₂O₃ etc.,from nanoparticle-polluted water system in large scale.The laboratorial and industrially viable technique can produce green nanoseparation from corrosive acid mixtures composed of carbon nanotubes.We demonstrated that the separation method is based on flocculation of arrayed nanotubes triggered by both chemical bonding and physical absorption（i.e.,Van der Waals and statistic interaction）.Interestingly,well-patterned ’carbon nanotube islands’ with a diameter of 1～5 microns and ’carbon nanotube rods’ with～1μm diameter,5～15-μm length were found on a modified glass surface,which may pave a new assembly way for nanoparticles.100nm～500nm length MCNTs-IL with a liquid-like behavior and an excellent thermally stability was obtained.It is noticeable that ca.6.5nm thickness shell model with an ionic,perpendicular bilayer structure on the CNTs surface were verified.This finding will offer a new practical method to process "solid CNTs" or polymer/CNTs composites like macromolecules,colloids or even solutions.Our quasi 1D PEG-MCNTs nanofluids behaved an unpredicted rheology behavior greatly different from the reported 0D nanostructures.Namely,highly viscous longer PEG-MCNTs system exhibits a liquid-like behavior throughout all the temperature range of 20-80℃,but low-viscous shorter PEG-MCNTs fluids behave as an unexpected elastic solid and even can give a solid-liquid transition at 56.7℃.Our model gives the quantitative relation（1/J·x = K·exp（-Ea/RT）or a/x= K’·exp（-Ea/RT））) between functionality density,aspect ratio and volume fraction and bulk rheological response.Our finding will be very attractive,according to the above quantitative relation,because the novel controlled rheological nanofluids can be achieved via a very simple oxidation technique.And these viscoelasticity controllable nanofluids will find important applications in sensors,nanodevices,and nanocomposites and so on.更多还原