Study On The Dispersibility Of Multi-walled Carbon Nanotubes

As an one-dimensional nano-material, carbon nanotubes(CNTs) have a unique structure and characteristics, including excellent mechanical properties,good electrical and thermal conductivity. Studying on the dispersibility of CNTs can alleviate the agglomeration of CNTs during dispersion, which is beneficial to take advantage of intrinsic characteristics of CNTs and promote the development of micro electromechanical devices and polymer/CNTs nanocomposites.In this thesis, the surfactants were used to modify the surface of multi-walled carbon nanotubes(MWCNTs) with non-covalent bonds. The stable and homogeneous dispersion of individual MWCNTs were prepared, and the dispersibility mechanism of MWCNTs was analyzed.Firstly, the MWCNTs were purified by the multi-step purification methods comprised of toluene ultrasonic, liquid phase reflux and mixed acid ultrasonic.The relative optimal experimental scheme was obtained through investigating the parameters of the purification experiments. The impurities contained in the purified MWCNTs were obviously decreased. At the same time, the experimentwas completed on the covalent bond surface modification of MWCNTs.Hydroxyl, carboxyl and other oxygen-containing groups on the surface of MWCNTs sample were detected, which can improve the chemical activity and the dispersibility of MWCNTs.Secondly, fullerenols were synthesized by the modified aqueous acid method. The results show that the products have a high degree of purity.Because of fullerenols surface contain hydrophilic hydroxyl groups, it can dissolve in water to form an aurantiacus solution. In addition, the experiments of photodegradation characteristics results show that the photodegradation efficiency of Methyl Orange(MO) with fullerenols is nearly 10 times than that of fullerenes.Then, three kinds of surfactants were used to modify the surface of purified MWCNTs with non-covalent bonds, which could improve the dispersibility and stability of MWCNTs. The results are as follows: fullerenols > SDBS > PVP,which is due to different sizes of spatial structure of surfactants. The larger the spatial structure of surfactant, the greater the steric hindrance can be generated in the dispersion of MWCNTs, thus the dispersibility and stability of MWCNTs can be better improved. The stable and homogenous dispersions of individual MWCNTs based on fullerenols were prepared, and after 5 days, the sediment percentage of this dispersion is only 5.2%.Finally, the factors affecting the dispersibility mechanism of fullerenols,including the surfactant concentration and the PH value, were studied. Theresults show that the concentration of MWCNTs in solution can be increased by increasing the fullerenols concentration. However, the latter is not increased with previous one linearly. When the phenomenon of fullerenols self aggregation occurres, the MWCNTs concentration would no longer increase.Meanwhile, it can be clearly observed that the dispersibility of MWCNTs in alkaline solution is better than that of the acid solution owing to the difference of dissociative property of purified MWCNTs and the dispersibility efficiency of fullerenols.