Controlled Synthesis, Characterization And Applications Of Carbon Nanomaterials

Recently, carbon nanomaterials attract more and more attention because of their distinctive physical and chemical properties as well as potential applications in many high-tech fields, such as biomedical engineering, catalysis, energy sources, etc. Manipulated synthesis of nanocarbons is one of the most important sections of carbon nanoscience and nanotechnology, and the base to investigate the distinctive properties and applications of carbon nanostructures. In this thesis, carbon nanotubes, hollow carbon nanocapsules, carbon encapsulated iron nanomaterials (Fe@C) and carbon nanobelts are selectively prepared with the assistance of different nano-reactors assembled by surfactants. The possibility of Fe@C as the magnetically separable catalyst support is investigated. The work is now summarized as follow:A technique combining microemulsion polymerization and the subsequent carbonization process is proposed for the selective synthesis of carbon nanocapsules, carbon nanotubes and carbon encapsulated nanoparticles. A quaternary microemulsion composed of CTAB (cetyltrimethylammonium bromide)/water/cyclohexane/n-pentanol is chosen as the nano-reactor with resorcinol (R) and formaldehyde (F) as the reactant monomers. The morphologies, structures and components of the as-made carbons are investigated by TEM, EDX, XRD, Raman, FT-IR and TG techniques. The experimental parameters such as the molar ratio of water to CTAB, the concentration of CTAB, the feeding amount of R and FeCl₃, and the solvothermal treating time and temperature are addressed. This method may provide an alternative synthetic route for the controllable preparation of carbon nanomaterials with different morphologies that are of great potential in many high-tech fields.Carbon encapsulated iron nanomaterials have been successfully synthesized by pyrolyzing RF polymer/iron oxalate composite in flowing hydrogen. Microemulsion polymerization of R and F is completed via a micelle-template technique with CTAB as the template agent. The as-made Fe@C exhibits well-constructed metal core/carbon shell structure with high BET surface area and superparamagnetic property. The effect of the experimental conditions on the formation of Fe@C is addressed, including iron salt feeding, carbonization temperature and the heating rate. Moreover, Fe@C supported Ru catalyst (Ru/Fe@C) is prepared through an impregnation process. Ru/Fe@C shows excellent catalytic performance for the oxidation of benzyl alcohol. The conversion of benzyl alcohol is 99.6% and the selectivity to benzaldehyde is 100% at 90°C, oxygen atmosphere with water-toluene biphasic system as the solvent. Ru/Fe@C can be easily separated and recovered by using a foreign magnetic field, and shows no obvious loss in catalytic activity after being reused for 4 times.Under the mediation of SDBS (sodium dodecyl benzene sulfonate) molecules, carbon-rich nanobelts (CNBs) are formed through carbonization of glucose under hydrothermal condition. The morphology evolution of CNBs has been investigated as the functions of the hydrothermal time and temperature. CNBs grow wider and thicker with the time prolonging and the temperature increasing. The EDX, FT-IR and XPS analysis confirm that there are functional groups abounded in as-made carbon framework. A possible growth model of CNBs is proposed and discussed in terms of the process parameters.Bamboo-shape and fishbone-like CNTs are selectively prepared by catalytic decomposition of acetylene over Fe-based catalysts that are prepared by SDBS-stabilized colloid chemical method coupled with calcination treatment. XRD analyses and TEM studies indicate that Fe catalysts result in the formation and growth of bamboo-shape CNTs, while Fe₃O₄ catalysts lead to fishbone-like ones. The factors in determining the morphology of the products and the growth mechanism of carbon nanotubes are addressed. Furthermore, simultaneous production of microsize hollow and solid carbon spheres is successfully achieved via non-catalytic chemical vapor deposition of acetylene. The unique feature is that the as-made two ball-like carbons can be collected separately as two individual products. The parameters such as the reaction temperature and the composition of the carrier gas are found to be critical for the formation of microsize hollow and solid carbon spheres.A polyoxometalates (POMs)-assisted hydrothermal system is developed for the modification of activated carbon (AC). The AC sample (AC-3) modified with hydrothermal treating for 3 days exhibits good adsorption capability, with thiophene removal ratio of 39.6%, much better than that of raw AC sample (11.8%). By adding SDBS, the hydrothermal reaction time can be reduced to 1 day, with the as-modified AC even showing a higher thiophene removal efficiency (50.7%) than that of AC-3. The functional groups and the porous structure are simultaneously responsible for the desulfurization performance of AC.