24. March 2016 at 15:15 in Physicum's aud A106 Jay Mondal will defend his doctoral theses "Novel corrosion protective nanostructured composite coatings".
Prof Väino Sammelselg, Institute of Physics, University of Tartu
Prof. Mario G.S. Ferreira, University of Aveiro, Portugal
Dr. Malle Krunks, Tallinn University of Technology
In this thesis corrosion inhibition performance of graphene and graphene oxide based composite/hybrid coatings was studied. Graphene is a two-dimensional one-atom-thick sheet of carbon having hexagonal lattice, and it is a basic structural unit of graphite. Graphene has proven to be one of the most popular advanced materials in recent developments. This carbon material is widely studied for advanced applications starting from energy harvesting to nanoelectronics and finishing with drug delivery because of many extraordinary properties of it. Among all of the properties the atom/ion barrier property was one of the most interesting for this work. Some studies to use graphene or graphene-based materials as a barrier sheet were published before starting this work and some appeared during the run of this investigation. Lately, the development of graphene and graphene oxide based functionalized biocompatible barrier coatings attracts a great attention among scientists and probably industrialists as well. But the use of graphene oxide/reduced graphene oxide nanoplatelets for corrosion protection of metal alloys was practically not studied before this work, despite the facts that the ideas of preparation the materials were known already decades, and as row material relatively cheap powder of natural graphite can be used. In this thesis the barrier properties of graphene/graphene oxide based nanostructured coatings, including composite and hybrid coatings were investigated towards corrosion protection. Investigations were carried through using different strategies: for the preparation of thin protective coatings spin-coating, electrochemical deposition and atomic layer deposition (ALD) techniques were used. For the corrosion inhibition performance studies of synthesized graphene oxide and reduced graphene oxide the hybrid coatings of graphene oxide-polypyrrole and the composite coatings of graphene-metal oxide laminates were prepared. The extent of protection ability of the coatings deposited onto AISI type 304 stainless steel and Ti-6Al-4V alloy substrates was studied thoroughly by electrochemical methods, as open circuit potential and Tafel plots, voltammetry and electrochemical impedance spectrometry, and tested by standard ASTM G48 A and long-time immersion tests in salt solutions. The studies revealed that prepared graphene and graphene oxide based hybrid and especially composite coatings well inhibit corrosion of the metal substrates. This definitely increases lifetime and stability of the metal details and equipment made from these materials, helping to preserve the materials and energy, thus helping to develop also a more sustainable society.