This thesis presents the results of experimental investigations of single-walled carbon nanotube (SWCNT) and nanobud synthesis. These carbon nanomaterials were synthesized by two different methods based on CO disproportionation on the surface of iron particles produced by hot-wire generator and ferrocene decomposition methods. Studies of CO disproportionation in the presence of etching molecules (H2O and CO2) led to the discovery of a novel hybrid carbon material — SWCNTs covered by covalently bonded fullerenes — carbon nanobuds. The reagent concentrations required for nanobud synthesis were found to be between 45 and 245 ppm for H2O and between 2000 and 6000 ppm for CO2. The growth mechanism of the nanobuds and their properties were examined. On the basis of in situ sampling investigations, the kinetics of the SWCNT growth was studied. For temperatures of 804, 836, 851, and 915 °C, the average growth rates were found to be 0.67, 1.11, 1.01, and 2.70 µm/s, respectively. It was found that the growth rate constant complies with the Arrhenius dependence with an activation energy of Ea = 1.39 eV, which can be attributed to the diffusion of carbon atoms in the solid iron catalyst. A new method for separating bundles and individual SWCNTs is proposed. This method is based on the fact that bundled SWCNTs coming from the reactor are charged, while individual SWCNTs remain electrically neutral. Studies of the charging phenomenon revealed that SWCNT bundles were charged (up to 99%) and could carry up to 5 elementary charges. It is proposed that SWCNT bundles were positively charged due to electron emissions and negatively charged due to the emission of impurities from the surface. As a potential SWCNT application, a simple and direct thermo-compression method for integrating SWCNT films with adjustable thicknesses, transparency, and conductivity into polymer films is demonstrated. The produced SWCNT/polyethylene composite films exhibited good optical transparency and conductivity as well as high mechanical flexibility. SWCNT/polyethylene thin films demonstrated excellent cold electron field emission properties.
|Julkaisun otsikon käännös||Aerosol synthesis of carbon nanotubes and nanobuds|
|Tila||Julkaistu - 2010|
|OKM-julkaisutyyppi||G5 Tohtorinväitöskirja (artikkeli)|