AFM studies of the Metallicity of Single-walled Carbon Nanotubes and Corrosion Inhibitor Adsorption.

摘要

Two families of novel materials, carbon nanotubes and corrosion inhibitors, were studied in this dissertation research. Their unique structures and properties were analyzed using atomic force microscopy in conjunction with other optical spectroscopies. Applications of atomic force microscopy were developed to measure the dielectric responses of nanomaterials, operate in aqueous environments and for removal of adsorbed molecules.;The heterogeneity of carbon nanotube samples has hindered their application and further development. A scanning probe microscopy assay has been established to differentiate between metallic and semiconducting nanotubes as well as to quantitatively determine metallicity; this was based on the different dielectric responses of metallic and semiconducting nanotubes. The metallic contents of multiple nanotube samples with various metallic-to-semiconducting ratios were determined using this method, the results being further confirmed by UV-Vis and Raman spectroscopy. This assay can provide a rapid method for evaluation of the effectiveness of selective nanotube synthesis and separation methods. The technique can be extended for the study of the dielectric properties of other nanomaterials.;Based on the different electronic properties between metallic and semiconducting nanotubes, a microwave irradiation effect directed towards the preferential etching of metallic nanotubes was further studied. Irradiation was found to cause the fracturing of a nanotube-film coated glass substrate, indicating nanotubes can absorb microwave energy and convert it to heat. THz transmission and Raman spectra show that the metallic content decreased after irradiation as particular spectral features decreased in intensity. UV-Vis absorption spectra indicated that the decreased metallicity was not solely due to the complete decomposition of the nanotube structure, but was affected by preferential oxidation or defect induction in metallic nanotubes.;The adsorption structure, film thickness, penetration force and removal force of adsorbed corrosion inhibitors were studied in aqueous solution. The structure and thickness of inhibitor films was found to depend on their concentration, bulk pH, solution ionic strength and surface properties. The measured force for penetration of an inhibitor film and removal of inhibitor molecules was of the order of 1∼10 MPa, indicating inhibitor molecules cannot be removed by fluid flow alone. This is the first time that the adsorption structures of inhibitors on metal surfaces were directly visualized and the mechanical properties of adsorbed inhibitor films quantitatively measured.