The Preparaiton And Characterization Of The Xinjiang Coal-based Carbon Nanotubes

The coal resources are rich in Xinjiang, but most of them only utilized as industrialfuel. It is very important to achieve the efficient utilization of coal. Carbon nanotubes(CNTs) were widely researched due to the unique mechanical and electrical properties.CNTs were synthesized using three different types of coal (Dahuangshan, Heishan,Kuche) from Xinjiang, and the influence of coal as carbon source on the production ofCNTs was investigated. Direct current arc discharge was employed for the synthesisusing different currents and pressures. Different atmospheres were tested in the arcdischarge synthesis including argon, helium and nitrogen. Nickel or its mixture withcobalt, ferrous sulfide was used as catalysts in the DC arc discharge process. The specificwork is as follows:First of all, The starting material, i.e., coal, were do some pretreatment such ascrushing, drying, and then were investigated by thermogravimetry and X-ray diffraction.In addition, the composition of the three types of coal was tested by industrial analysisand elemental analysis. Conduct an experiment with relatively high fixed carbon contentof coal in heishan and kuche. The coal-based carbon anode was prepared by ball millingof the coal followed by mixing with coal tar, molding and carbonization. Condersideringthe anode consumpsion rate and product yield at different currents and pressures, the claoof kuche was the optimal carbon source in the DC arc carbon nanotubes. The coal-basedcarbon anode was prepared by ball milling of the coal followed by mixing with coal tar,molding and carbonization. Considering the anode consumpsion rate and product yield atdifferent currents and pressures, the coal of kuche was the optimal carbon source in theDC arc carbon nanotubes. The suitable discharge current and appropriate atmospherepressure were70A and0.065Mpa.The CNT samples obtained under different synthesis conditions were purified by acidwashing and studied by field-emission scanning electron microscopy, high resolutiontransmission electron microscopy, Raman spectroscopy and fluorescence spectroscopy.After comparing different starting coal and catalysts, it was found that the highest yieldof CNTs was obtained using Kuche coal with12%of mixture of the nickel and ferrous sulfide, indicating that the catalyst strongly affects the yield of CNTs. Comparing thesynthesis atmosphere, the CNTs obtained under argon have a more uniform structure andless defects. In contrast, the CNTs obtained under nitrogen or helium have less uniformstructure. The average diameter of CNTs achieved under nitrogen is larger than that ofCNTs obtained under helium, but smaller than under argon. The results showed that thestructure and the diameter distribution of CNTs are different when different gases wereused during synthesis, indicating that the diameter of CNTs is dependent on theproperties of the gas. The fluorescence spectra showed a good agreement with Ramanstudies and confirmed the results on the structure and morphology of the CNTsdetermined by other techniques. The mechanism on the growth of CNTs and theirstructural differences were discussed. As a whole, we tested and demonstrated thefeasibility of CNT synthesis using different types of coal by direct current arc dischargemethod under different atmospheres, and compared the complexity and product quality ofdifferent synthesis processes.Finally, the dipping of kuche coal is also discussed. There is little differencebetween dipping coal and undipping coal by infrared and thermogravimetry. Theproducts were studied by field-emission scanning electron microscopy, Ramanspectroscopy. The result showed dipping the coal has some infulence on the growth ofCNTs.