Preparation Of Novel Carbon Nanostructured Materials By Chemical Vapor Deposition (CVD) Method

As a new carbon material in the 21 st century,carbon nanotubes(CNTs)have excellent optical,electronic,magnetic,thermal,chemical and mechanical properties,which has become a hotspot in recent decades.There are many methods for the production of CNTs.Among them,chemical vapor deposition(CVD)is the most popular and promising method for the production of CNTs in recent years,because of its simple equipment,simple operation and low cost.In this thesis,we used ceramic boat on quartz boat as substrate,benzene or anhydrous ethanol as carbon source,thiophene as the growth promoter,ferrocene as the catalyst precursor,hydrogen as the reaction carrier gas and the buffer gas,to produce novel nanocarbons by chemical vapor deposition.We employedscanning electron microscopy(SEM),transmission electron microscopy(TEM),energy dispersive spectroscopy(EDS)and Raman spectroscopy to measure the morphology,diameter,the number of layers,quality,composition and so on.By adjusting the experimental parameters,such as carbon source flow rate,hydrogen gas flow rate,and pyrolysis temperature,we studied the influence of various experimental parameters on novel nanocarbons.We successfully synthesized a novel carbon nano-hoist structural material.At the same time,we also carried out a preliminary study on the purification of this kind of novel nanocarbons.Firstly,we explored the effects of carbon source flow,hydrogen flow rate and pyrolysis temperature on the growth of carbon nanotubes.We found that the increasing flow rate of the carbon source is not favorable to the growth of carbon nanotubes.Under certain experimental conditions,with increasing flow rate of the carbon source,but amorphous carbon and impurities increased,and the quality of CNTs declined.Similarly,hydrogen as a buffer gas is essential for the production of carbon nanotubes,when the hydrogen flow rate is too large,to the quality of the declines because of the production of more by-products.In addition,the pyrolysis temperature is also an important condition for the growth of carbon nanotubes,whichcan not be ignored.When the pyrolysis temperature is too low,the carbon source does not release enough high-activity carbon atoms and catalyst particles,then carbon nanotubes can not be obtained.If the pyrolysis temperature is too high,the quality of carbon nanotubes will also decline.Secondly,by adjusting the experimental conditions,benzene or absolute ethanol as carbon source,we have synthesised a novel carbon nano-gourd structural materials.Transmission electron microscopy(TEM)images show that the novel structure materials are some parts of the carbon nanotubes with graphite-coated carbon nanotubes.The carbon nanotubes can be single-walled carbon nanotubes(SWCNTs)or multi-walled carbon nanotube(MWCNTs).Finally,for as-prepared nanocarbons,we can remove the catalyst metal particles,amorphous carbon and other carbon particle impurities through acid treatment and air oxidation by acid treatment and oxidation treatment.We also found that oxidation temperature and oxidation time play a great role on the purification of nanocarbons.If oxidation temperature is too high and oxidation time is too long the structure of nanocarbon will be destoryed.On the contrary,we can not achieve the desired purification effect.Through preliminary exploration,we found that the oxidation temperature of 380?,with the oxidation time of 3.5h can be remove most of amorphous carbon and maintain the basic structure of nanocarbons.