The Synthesis And Field Emission Properties Of Carbon Nanotubes

Since the discovery of carbon nanotubes in 1991, the investigation on carbon nanotubes has become a hot topic in the world. Due to the ultimate form of single-wall carbon nanotubes (SWNTs) in the carbon family with special structure, SWNTs have excellent properties and wide potential application. However, the limitation of large-scale production has restrained the development of the research on their application. The field emission properties is most important among the applications. The factor of electric field enhancement is the important parameter that influence emission characteristics of carbon nanotube arrays. The mechanism of the electric field enhancement being influenced by the nanotuble size and the density of nanotubes is studied. So the study of the mechanism of the electric field enhancement is important to enhance the emission characteristics; The technique about the realignment of purified CNTS is meaning for the field emission characteristics and the preparation of cold cathode.The single walled carbon nanotubes (SWNT) and SWNTs' bundle are produced by using the investigative experiment equipment of anode arc plasma to evaporate graphite rods containing Fe, Co, Ni catalyst. The characteristic studies through the XRD, Raman spectrum and the thermogravimetric analysis (TGA) proved that the products is the expected high quality SWNTs and bundles with homogeneous diameter, less-defection, high-purified and quasi-straight SWNT. At the end, the prime parameters in the synthesis process of anode-arc plasma evaporation method for preparing SWNTs has been concluded to be helium pressure 6.0×10~4Pa, arc current intensity 70A, the catalyst content of W(Fe):W(Co):W(Ni)=l:l:l, and with good cooling as well. The elastic modulus, density varied with the diameter of SWNTs has been presented.The relations of the factor of the electric field enhancement to the nanotuble size, the density of nanotubes and the field emission threshold voltage have been studied using a simple model of carbon nanotube arrays.The technology of the realignment of purified CNTS in the shear flow and in the mechanical stretching process is presented in this paper. The mechanism of the realignment of purified CNTs in the shear flow, electric field and strong magnetic field are studied using different theoretical models. PMMA/CNTs composite with well aligned CNTs along the stretching direction is synthesized using mechanical stretching method. The aligned CNTs modified PMMA/CNT composite present highly anisot ropic properties, as a result the composite showed higher conductivity, higher strength and higher mechanical draw ratios along the stretched direction than perpendicular to it. This experimental result is consistent with our theory analysis.