The Research About The Field Emission Properties Of Carbon Nanotube

Recent years,field emission display(FED) has attracted a lot of attentions because of its advantages such as high display quality,low power consumption and was considered to be one of the most promising next generation display technologies.The discover of carbon nanotubes(CNTs)attract many scientists's attention,carbon nanotubes can be used in many domain due to it have excellent mechanics,electricity and magnetics,carbon nanotubes have a high ratio in length-radius,low workfunction, good electrical conductivity and nanometer tip,it can emit electron long time in low voltage.So it have been considered a good field-emission cathode.Following the discovery of carbon nanotube,more and more efforts have been concentrated on the studies of carbon nanotube field emission display prepared by screen-printing thick film technology.The key of advanced performance is to improve the field emission properties of carbon nanotube based cold cathodes,but more essential research is to develop the new printable carbon nanotube based cold cathode materials, which are satisfied for the requirement of field emission display.The key for practicality is to improve the stability and uniformity of large-area field emission display.In this paper,we studied the purification and dispersion process of carbon nanotube at first. Then we focused on developing the printable carbon nanotube based cold cathode materials,used to fabricate diode carbon nanotube field emission display devices by screen-printing method.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 anisotropic 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.A hexagon pitch CNTs array vertical to the normal-gated of cold cathode Field Emission Display(FED) which would be useful for future application is simulated by solving Laplace equation in this article.The calculated results show that the intensity of the electric field is very strong near the top of the CNTs,and drops abruptly with the increasing of the distance from CNTs.The higher aspect ratio of the CNTs is,the stronger aroused field at the CNT top exists.The simulated results demonstrated that the emission current intensity can be increased highly by decreasing the normal-gated aperture.The results indicated that the electric field around the normal-gated cold cathode excludes with the CNTs' electric field each other,and the normal-gated makes the electrical field around the top of the CNTs concentrated.It also could be concluded that a higher gate voltage exerts a greater influence on the emission current which decreased with the distance of anode-cathode d increased.In brief,this paper dissertation screen-printing process and the theory of CNTs field emission.It is of significance to promote the development of CNTs field emission display.