Carbon Nanotube Field Emission Preparation And Properties Of Fluorescent Tubes

Field emission light source has drawn wide attention for its low power consumption, high brightness, long working-life and non-pollution. This paper focused on the practical research of carbon nanotube field emission fluorescent devices and the fabrication of anode fluorescent screen, carrying out the fabrication of ITO film anode, the coating of phosphor layer, as well as the assembling and testing of fluorescent tube.Firstly, ITO conductive anode films were fabricated on glass tube substrates by sol-gel process. The sol was prepared using indium nitrate, stannic chloride and acetylacetone. Then, the wet-films were prepared on glass substrates by dip-coating method. In the end, the ITO films were obtained after sintering process. The effect of various process parameters, including In3+ concentration, Sn-doped proportion, sintering temperature and time, as well as layer number of the film, on the structure, surface morphology and opt-electric properties of ITO films were studied and discussed. Certain conclusions were obtained as follow:(1) XRD results suggested that Sn was effectively doped into the lattice of indium oxide, and the ITO film has the Polyerystalline eubicbixbyitel In2O3 structure.(2) SEM results indicated that the surface of ITO films presented a porous structure accumulated by nano-particles.(3) The sheet resistance of ITO films decreased as the increase of In3+concentration in the sol. When In3+ concentration increased to a certain level, the uniformity of the thin film reduced, while the sheet resistance changed slightly. When In3+ concentration was 0.2 mol/L, the sheet resistance and the uniformity of the film reached to the best level.(4) The sheet resistance of ITO films decreased as the increase of the Sn-doped proportion. The sheet resistance changed slowly when Sn-doped proportion was higher than 5%, and It achieved the minimum when Sn doping ratio was 15%. The average visible transmittance of ITO films increased when the Sn-doped proportion increased.(5) The sheet resistance of ITO films decreased as the increase of sintering temperature and time, as well as film thickness. When the sample was sintering at 450℃for 8h, its sheet resistance reached the minimum value. The average visible transmittance of ITO films increased with the augment of sintering temperature and decreased with the increase of film thickness.(6) An anode ITO conductive layer of field emission fluorescent tube with excellent opt-electric performances was obtained in the end. The sheet resistance of the ITO film prepared by the same processing condition was 360Ω/□, and the average visible transmittance was about 82%.In addition, phosphor layers were fabricated by electrophoretic deposition. The effect of various process parameters, including phosphor concentration, electrolyte concentration, electrophoretic voltage and electrophoretic time, on the thickness and surface morphology of phosphor layers were analyzed. The best process parameters were obtained: the phosphor concentration was 10 g/L, the electrolyte concentration was 0.128 g/L, electrophoretic voltage was 150 V while the electrophoretic time was 2 min. An anode fluorescent tube with homogeneous surface and ideal thickness was fabricated at last.In the end, the carbon nanotube field emission fluorescent tube was assembled, lightened and tested in vacuum atmosphere. The results showed that carbon nanotube field emission fluorescent tube could be lightened instantly, and the light could be continuously modulated as well. When the anode voltage was 5kV, the brightness was 3519 cd/m2.