Carbon nanotube electronic structures as anti-corrosion coatings

A new concept of corrosion prevention is considered in this study. Diode-like and transistor-like structures have been fabricated and analyzed in the study of ionic flow through the resulting potential barriers. The structures were made of functionalized carbon nanotubes. Carbon nanotubes are known for many remarkable properties among which is being chemically inert. Taking advantage of this property, a study of corrosion of steel was undertaken.;In the first case study, successive layers of functionalized carbon nanotubes were deposited to form p-n junctions on steel substrates. It was demonstrated that the corrosion was indeed impeded by the potential barrier formed across an electronic p-n junction. Potentiodynamic measurements, Raman spectroscopy, impedance measurements and scanning electron microscopy with energy dispersive x-ray spectroscopy were used to assess the corrosion process. It was found that the layer ordering (p-n or n-p with respect to the metal electrode) determined the corrosion rate in de-ionized (DI) water. Only temporary resistance was found in the presence of 3.5 wt% NaC1 solution.;In the second case study, functionalized carbon nanotubes were drop-casted layer by layer to obtain transistor like p-n-p or n-p-n junctions. It was observed that the base voltage appreciably controlled the surface potential. The layer ordering determined the direction in which the surface potential of the steel substrate varied.;In the third case study, graphene was used as an intermediate layer between the steel substrate and the electronic p-n junctions. Graphene was also used as an intermediate layer between a steel substrate and a conductive polymer (polypyrrole) film. Here it was demonstrated that the monolayer thick graphene had a significant effect on the surface potential of the steel substrate. Also, graphene provided for an additional protection as determined by corrosion experiments.;In the fourth case study, bio-compatibility nature of carbon nanotubes was exploited. Single stranded deoxyribose nucleic acid was used to functionalize carbon nanotubes and obtain n-type semiconducting films. Electronic junctions were fabricated using these films as previously noted. The effect of bio-electronic p-n junctions was similar to the first case study, yet, by doing so, the potential for bio-ionic applications is made possible.