【作者】 马军；

【导师】 李效东；

【作者基本信息】 国防科学技术大学 ， 高分子化学与物理， 2009， 硕士

【摘要】 碳纳米管作为一种新型一维纳米材料,拥有优异的力学、电学、光学等性能,在高性能复合材料、先进阴极发射器、大容量超级电容器、高灵敏度传感器、废水处理、清洁能源、生物医药工程等领域具有巨大的应用潜力。但碳纳米管在复合材料或溶液等领域应用时易于团聚而难以均匀稳定分散,针对此问题的大量研究成果表明对碳纳米管进行化学修饰可有效改善其分散性能。本文在化学气相沉积法制备碳纳米管(CNT)的基础上,使用浓硝酸和丙烯酰氯对CNT进行化学修饰,制备了表面官能团化的碳纳米管,并对反应产物的结构和性能进行了表征和分析。利用经过化学修饰的碳纳米管和陶瓷先驱体聚碳硅烷(PCS)为原料制备了CNT掺混型聚碳硅烷,对其进行了表征和分析,并研究了该先驱体的流变性能。利用CNT结构中存在缺陷的特点,有望通过化学反应在其表面引入特定官能团,从而达到化学修饰的目的。本文以二茂铁和甲苯为原料,利用CVD法在约700℃制备了CNT,首先利用浓HNO3对其进行酸化氧化,研究了氧化时间对其结构和表面官能团组成的影响,发现浓硝酸对CNT具有较强的氧化、腐蚀作用,在酸化后的CNT中,氧含量急剧上升,生成了大量含氧官能团,为后续修饰反应提供活性点;浓硝酸对CNT具有腐蚀端帽、管壁的作用,造成CNT的结构发生变化。综合考虑产物的结构变化和官能团含量,选择使用经过24小时酸化氧化的CNT进行后续的化学修饰。利用丙烯酰氯对酸化氧化后的CNT进行化学修饰,研究了修饰反应对CNT形貌、官能团组成和结构的影响,制备了表面包覆聚丙烯酸的CNT。发现由丙烯酰氯生成了聚丙烯酸并覆盖在酸化氧化后CNT表面上、或填充在酸化氧化后CNT的孔洞中,因此降低了酸化氧化后CNT的比表面积。将表面覆盖聚丙烯酸的CNT与陶瓷先驱体溶液回流反应共混,制备了CNT掺混型聚碳硅烷,发现化学修饰有效地提高了CNT在有机先驱体溶液中的稳定分散程度;并对该陶瓷先驱体的流变性能进行了探索,研究了其粘度随温度和剪切速率的变化规律,为CNT掺混型聚碳硅烷在陶瓷纤维和陶瓷基复合材料中的应用奠定了基础。更多还原

【Abstract】 With the outstanding mechanical, electronic, optical and other properties, carbon nanotube is one of novel quasi one-dimension nanostructure materials and has attracted considerable attentions in the possible application fields of high-performance composites, advanced cathode emitter, large capacity super capacitor, high sensitivity sensor, liquid waste disposal, clean energy and biomedical engineering. However, carbon nanotubes tend to aggregate and are hard to homogeneously dispersed in solvent. A great deal of studies had proved that chemical modifications are significant ways to solve the problem. In this work, CNT was first prepared by the method of chemical vapor deposition route, and was then modified by chemical reactions with HNO3 and acryloyl chloride. Finally, the functionalized CNT was mixed with polycarbosilane to prepare a hybrid polymer precursor which may find applications in ceramic matrix composites.The chemical modifications of CNT are practically feasible because of the intrinsically existing defects, where will be the favorable sites for introducing functional groups. The CNT were prepared from pyrolysis of the mixture of ferrocene and toluene under about 700℃. Then the as-prepared CNT were treated in concentrated HNO3 for hours to introduce oxygen functionalization on CNT. The structrue was also changed in reaction. The result indicated that HNO3 has strong oxidation on CNT, and large numbers of oxygen-containing groups were created for subsequent modifications; a prolonged oxidative treatment leads oxidative opening of CNT. The density of functional groups is significant for further modifications, so the product of oxidized CNT which had treated in HNO3 for 24 hours was chosen to reflux with acryloyl chloride in subsequent functionalization procedure.The reaction between the oxidized CNT and acryloyl chloride was carried out. The analysis of final products of oxidized CNT reacting with acryloyl chloride implied that acryloyl chloride had polymerized on the surface of CNT and converted to poly(acrylic acid), CNT were consequently wrapped in the poly(acrylic acid). This procedure make the specific surface area of CNT decreased sharply.Then the poly(acrylic acid) encapsulated CNT refluxed with polycarbosilane to make hybrid precursor. It’s evident that the chemical modification of CNT effectively promoted its dispersity in the toluene solution of hybrid precursor. The rheology of hybrid precursor was preliminary studied, and the principle of it’s melt viscosity dependent on temperature and shearing rate were investigated for prospective applications in ceramic fibres and ceramic matrix composites.更多还原