Studies On The Fabrication And Characteristic Of Defect-abundant/Ultrashort Carbon Nanotubes And Supported Catalyst

Carbon nanotube (CNT) is a novel carbon material with unique structure and properties, and has drawn much attention as potential applications in many areas. In this paper we make systematic research new properties of CNTs and the preparation of carbon-matrix composite materials, and we get some innovative results. It mainly contains several parts as follows:1. The low temperature (700℃) prepared carbon nanotubes (CNTs) were annealed in the high vacuum after purification, the defunctionalized CNTs (DF-CNTs) were obtained. RAMAN, HRTEM, XPS and BET show that the O/C ratio is decreased, the I_D/I_G and the BET is increased. The DF-CNTs were confirmed the abundant defects of CNTs. The photocatalytic experiments were also investigated through the degradation of H₂O₂, the result shows that the defect-abundant CNTs (DF-CNTs) have the photocatalytic property.2. Short carbon nanotubes (S-MWNTs) were prepared by thick HNO3/H2SO4 chemical oxidation cutting, when it was filtrated through 0.1μm Teflon filters, the Ultra S-MWNTs (US-MWNTs) were obtained from the filtrate, and the luminescence spectra of the US-MWNTs were discovered. This result indicates that the luminescence properties of MWNTs are strongly affected by the tube length. The more shorten of MWNTs, and the better carboxylic passivation of the nanotubes, the more intense luminescence emissions.3. TiO₂ /short MWNTs (S-MWNTs) composite was prepared by the sol-gel method using isopropyl alcohol as the solvent. The result s showed that the TiO₂/ S-MWNTs composites with 1 % mass ratio of S-MWNTs to butyl titanate had the best photoactivity. X-ray diffraction (XRD) shown that TiO₂ crystal was not changed with combined to a small quantity of S-MWNTs. UV-vis absorption spectra shown that the nanocomposites exhibit a very broad absorption, an interesting feature for the nanocomposite is a slight blue shift of band edge absorption with respect to TiO₂ nanoparticles.4. Flowerlike Cu₂O nanostructures have been successfully prepared by a low solution phase method. Control experiments were carried out to demonstrate that the concentration of NaOH and CTAB play key roles in the formation of the as-synthesized nanoflowers. The results indicate that the growth of the nanoflowers were governed by a nucleation-dissolution-recrystallization growth mechanism. The four different growth stages are involved: (i) generation of primary nanoparticles of Cu₂O; (ii) the dissolution of the primary Cu₂O; (iii) the recrystallization of short Cu₂O protuberances; and (iv) crystal aging of Cu₂O and formation of flowerlike nanostructures.5. A wet chemical method for synthesizing MWNTs beaded with Cu₂O nanospheres has been developed. The results shown that the chemical oxidation using the mixed acids solution can introduce various functional groups at the defect sites of the nanotubes wall, these functional groups not only enhance the solubility of the MWNTs, but also can act as nucleation sites for metal clusters. The properly surfactant of PVP is necessary for the formation of Cu₂O nuclei and further growth on MWNTs; this would decrease the activation barrier towards heterogeneous nucleation, or alternatively increase that towards homogeneous nucleation.