Synthesis Of Carbon Nanomaterials And Their Applications In Transparent Conductive Films And Field Emission Displays

Carbon nanomaterials, such as carbon nanotube (CNT), graphene, have attracted much attention, because of their unique structures and extraordinary mechanical, optical, thermal and electrical properties. CNT and graphene have been widely investigated for potential applications, such as transparent conductive films and field emission cathodes.This dissertation focused on the synthesis of carbon nanomaterials and their applications in photoelectric devices. The investigation contains the novel method for the synthesis of two-dimensional carbon nanomaterial, the fabrication of carbon nanomaterial films by vacuum filtration, the transparent conductive properties of the filtered carbon films, the field emission properties of the filtered and screen-printed carbon films, and the driving system for the CNT field emission display (FED).The work mainly includes the following aspects:1) The discovery of the formation of two-dimensional nanomaterials through pulsed laser exfoliation, and the mechanism description.When the pulsed laser interacted with the spin-coated poly(phenylcarbyne) film in a vacuum chamber, the laser plume occurred and a silicon substrate was used to collect the ablated materials. By controlling the laser energy, laser wavelength and pressure, different carbon nanostructures were obtained on the silicon substrates, such as amorphous carbon, two-dimensional carbon nanosheets, diamond-like carbon. The experimental parameters for the formation of two-dimensional nanomaterials were suggested as:a plane and continuous target surface, the photon energy of the laser smaller than the bond energy in the polymer, and an appropriate laser fluence.This study reveals a novel route of forming two-dimensional carbon nanosheets by pulsed laser for the first time, and has significantly contributed to the field of laser-assisted nanotechnology.2) The discovery of the synthesis of graphene by pulsed laser exfoliation. The formation of graphene by liquid-phase pulsed laser exfoliation and its application in transparent conductive films.Few-layer graphene was formed through pulsed laser exfoliation of highly ordered pyrolytic graphite (HOPG) in a vacuum chamber. The laser interacted with the HOPQ and a silicon substrate was used to collect the ablated material in laser plume. As the laser fluence increased, different carbon phases, amorphous carbon, few-layer graphene, and thin graphite films, were obtained. The mechanism was explained as the laser-induced mechanical process leaded to the compression and expansion of HOPG surface, resulting in the exfoliation of graphene sheets.Liquid-phase pulsed laser exfoliation offers an effective way to collect the graphene. Graphene suspension was obtained and transparent conductive graphene films were fabricated by vacuum filtration.3) The fabrication and properties of transparent conductive CNT and graphene films by vacuum filtration.The film fabricated by vacuum filtration has uniform surface, and the thickness is easy to control. Transparent conductive CNT and graphene films were fabricated by vacuum filtration. The film transfer process was explained by interfacial binding energy between different materials. To further improve the transparency and conductivity of the films, effort will be put into the modification and composition of the carbon materials.4) The investigations on the electron field emission properties of CNT and graphene films fabricated by vacuum filtration and screen printing.Electron field emission properties of CNT and graphene films fabricated by vacuum filtration were studied by changing filtration volumes. A comparative study on the electron field emission properties of carbon films prepared by vacuum filtration and screen printing was carried out. Comparing with the screen-printed carbon films, filtered carbon films showed lower turn-on field, higher enhancement factor, better emission spot density, longer lifetime, and greater adhesive strength to substrates. This study reveals a potential route of the filtered carbon films as field emission cathodes. 5) The driving system for large-scale CNT FED.The driving system was designed for the40-inch CNT FED. The driving voltage for the diode-type FED is around300V. Based on digital visual interface, decoding system, field programmable gate array control system, and high voltage driving circuit, the driving system for the large-scale diode-type CNT FED was developed, and the dynamic display was realized.