Fabrication Of Carbon Nanotubes Composites And Nanotubes Using Carbon Nanotubes As Templates And Studies Of Their Properties

As an excellent 1D nanomaterial. carbon nanotubes (CNTs) with an unique structure and chem-physical properties have been widely applied in various areas. Among them, carbon nanotube composites have attracted increasing interest because of the combination of the CNTs and other materials may lead to a successful integration of the properties of the components in the new hybrid materials. In our work, a series of carbon nanotube composites such as Ni/CNT, hollow CoO/CNT, Si/CNT and TiO2/CNT have been prepared using carbon nanotubes as supports. Moreover, the SnO2/TiO2, SnO2/SiO2 composite nanotubes have also been fabricated using carbon nanotubes as templates. Furthermore, the structure, morphology and properties of these composite materials have been characterized and studied. The research contents as followed:1. The modified substrate enhanced electroless deposition (SEED) process was used for preparing the Ni/CNT composites. The size of the Ni NPs can be controlled by varying the concentration of the NiSO4 solution. Moreover, we found that the Co/CNT composites converted into hollow CoO/CNT composites due to the Kirkendall effect when we tried to prepare the Co/CNT composites by the modified SEED process. A new route for the synthesis of Si/CNT composites by a low-temperature magnesiothermic reduction process was presented. Moreover, the size of the Si NPs could be controlled by varying the silica (SiO2) thickness of SiO2/CNT precursors.2. A two-phase thermal approach was used to prepare the TiO2/CNT composites which have TiO2 nanoparticles with a narrow size distribution and a uniform dispersion on the CNT surface. We studied the influence of the ratio of water and oil on the amount of the TiO2 NPs load on the CNTs and the reaction time on the size of the TiO2 NPs. The amount of TiO2 NPs loaded on the CNTs decreased no matter the water content either too much or too little. The size of the TiO2 NPs increased with the increase of reaction time. In addition, we also investigated the influence of the CNTs surface defect on the photo-catalytic activity. In order to get the CNTs with the different number of defect, we treated the CNTs with the concentrated nitric acid for 1 h,4 h,8 h and 12 h. respectively. The number of defects was determined by XPS to measure the oxygen content of the CNTs. The oxygen content increased from raw 1.25% to 8.2% with increasing the acid-treatment time. The composite prepared with the TiO2 and the CNTs (8 h) has the best photo-catalytic activity.3. The TiO2 nanotubes and SnO2/TiO2 nanotubes were prepared using CNTs as templates. The structural and morphological characterizations of the TiO2 nanotubes and SnO2/TiO2 nanotubes have been carried out using XRD, SEM, TEM and XPS. The PL spectra and X-ray photoelectron spectroscopy (XPS) method indicated that the separation rate of photo-induced electron-hole pairs was improved through SnO2 NPs combined with the TiO2 nanotubes. The SnO2/TiO2 nanotubes have a higher photo-catalytic activity than P25. suggesting that it would be promising as a new photo-catalytic material in the photo-catalysis area.4. The two kinds of composite nanotubes. SnO2/SiO2(in) and SnO2/SiO2(out), were synthesized using CNTs as templates. They all possessed a narrow size distribution, a large specific surface area, and good thermal stability. UV-visible absorption spectra of the SnO2/SiO2 composites present a blue-shift with the decrease of particle size, which could be attributed to the quantum size effect. The photo-catalytic reaction showed that the ) has the same photo-catalytic ability as the P25.