Chemical Modification, Structure Characterization And Properties Study Of Carbon Nanotubes

In this thesis, to begin with, solube carbon nanotubes were prepared and characterized. Then, the most optimized condition to modify the carbon nanotubes while keeping the inherent properties of MWNTs as much as possible was investigated. The following results were obtained:1. A series of octadecylamine (ODA) grafted multi-walled carbon nanotubes (MWNT) were prepared and characterized by NMR, FTIR, DSC and XRD. It is revealed that the ODA chains grafted on MWNT are partially crystallized, though the packing structure is not as perfect as the pure ODA. It is believed that ODA prefer to react at some active sites, such as the tube-ends and the defects on the sidewall of MWNT. A quantitative NMR technique was developed to determine the weight percent of ODA in modified MWNT. The relationship between the content of ODA and the solubility of soluble MWNTs is discussed.2. Multi-walled carbon nanotubes (MWNTs) were oxidized and shortened with a mixture of concentrated sulfuric and nitric acids under sonication, to introduce carboxyl and hydroxyl groups onto MWNTs. TEM, resistance measurement and 1H NMR were carried out to study the effect of oxidation on the area ratio, resistivity and the amount of hydrogen of the modified MWNTs. The results show that 10 h of oxidation may be the most favorite condition to shorten the carbon nanotubes and introduced enough functional groups while keeping the inherent properties of MWNTs as much as possible.3. Effects of oxidation time on the electromagnetic shielding characteristics of carbon nanotubes were investigated by Network Analyzer. A 6h oxidation time can not destroy the electromagnetic shielding characteristics of carbon nanotubes obviously. The reflect characteristic of the modified carbon nanotubes decreased, while the absorption characteristic increased reversely.