Synthesis And Characterization Of Carbon, Lead Oxide And Hydroxide Nanostructures And Their Physical Properties

Nanostructured materials have aroused much attention due to their remarkable properties different from bulk materials. They have many potential applications in physical, electronic, chemical and biological field. However, to achieve the pratical application of nanostructured materials, it is important to develop simple, cost-effective and good-reproducibility method to sythesis nanomaterials. Therefore, in this thesis, we emphasize to investigate and develop simple, cost-effective and good reproducibility route to prepare nanoscale materials. The detailed contents, results and conclusions of this thesis are listed as follows:1. The synthesis of carbon nanostructures, such as carbon nanofibers, multi-walled carbon nanotubes and their arrays, iron-filled carbon nanotubes and their arrays, and single-walled carbon nanotubes, by employing ethanol floating catalyst chemical vapor deposition (EFCCVD). Our results show that the formed nanoscale iron particles with different sizes could be seperated and deposited on different position in a furnace tube under gravity and viscous resistance of carrier gas. Utilizing this phenomenon, we can achieve the synthesis of carbon nanofibers, multi-walled carbon nanotubes and arrays (or iron-filled carbon nanotubes and arrays), single-walled carbon nanotubes at the same time. More important, the single-walled carbon nanotubes can be deposited in the low-temperature (<400℃) area at the growth temperature of 900℃in this process. This gives opportunity to deposit the single-walled carbon nanotubes on the substrates that can not suffer from the high growth temperature, such as ITO glass. So, single-walled carbon nanotube film electrodes on ITO glass, which can apply to dye or quantum-dot sensitized solar cell as a carbon counter-electrode, can be easy to obtain by this simple process. Iron-filled carbon nanotubes and their arrays can be synthesis by EFCCVD with a great excess of ferrocene and their magnetic properties are characterized by vibrating sample magnetometer. The obtained iron-filled carbon nanotubes and arrays have an average coercivity of about 257.05 and 589.97G, respectively, which are higher than that for the bulk polycrystalline iron and nanocrystalline iron.2. The possible morphologies of multi-branched carbon nanofibes have been discussed. For Y-shaped carbon nanofibers, there are four basic possible morphologies; for multi-direction carbon nanofibers, the possible number of branch fibers is a positive integer. Interestingly, we have observed these multi-branched carbon nanofibers in our experiments. The number of branch fibers of multi-direction carbon nanofibers is 2,3,4,5 observed in our experiments. The formation of these multi-branched carbon nanofibers may be related to the unstability of diffusion flames. To improve the stability of flames, we develop a new simple method of stably confined diffusion flames (SCDF) to synthesis carbon nanostructures. In this mehod, the flames only burn in a confined space and no flames exists out of this confined space. This confined flame has high stability that can offer a steady condition to grow carbon nanotubes. By employing thiophene/ethanol as fuel for SCDF, carbon nanotubes and their arrays, single-walled carbon nanotubes can be synthesized with good reproducibility.3. The synthesis of PbO nanorods on an ITO substrate by DC electrochemical deposition has been investigated. Compared with previous report on the electrochemical deposition of PbO nanorods on stainless steel substrates, massive PbO nanorods were obtained with good reproducibility. The optical property of the PbO nanorod film is characterized by UV-vis absorption spectrum and the bandgap of PbO nanorods can be inferred to be 2.85eV according to UV-vis absorption spectrum. The PbO nanorod films on ITO glass can be applied to fabricate dye-sensitized solar cell as a light electrode. The open-curcuit voltage of a dye-sensitized solar cell based on PbO nanorod films can reach 0.5V. The growth mechanism of PbO nanorods prepared by DC electrochemical deposition has been discussed. The intermediate state during the formation of PbO nanorods is obtained by a simple washing of primary deposits with absolute ethanol. According to the obsvervation on the intermediate state, we have proposal a possible model to describe the growth of the PbO nanorods.4. A new simple method to synthesize lead hydroxide nanorods by solution-phase reaction has been developed. The growth of lead hydroxide nanorods is due to the adsorption of chloride ions on the certain crystal planes. So, to obtain lead hydroxide nanorods by solution-phase reaction of lead nitrate with alkali, chloride ions is need to be added into lead nitrate solution. The concentration of chloride ions has a dramatic effect on the morphology and microstructure of the precipitates obtained from the lead nitrate and alkali solution, and this effect has been intensively disscussed. Futher more, a possible growth model has been proposed according to our experimental results. The microwave dielectric property of lead hydroxide nanorods is measured by vector network analyzer. The results indicate that lead hydroxide nanorods have a low dielectric loss tangent and they can be applied to fabricate multi-layer microwave absorption materials as transition layers.In the finality, the problems requiring further studies are discussed.