Graphene-based Coatings for Heat Exchangers

Abstract: This master thesis is a part of a larger interwork between SP, KTH and Alfa Laval funded by the SIO graphene programme, which end goal is to formulate an anti-corrosion coating based on graphene or graphene related materials (GRMs). The investigation is partly based on an article “Novel anticorrosion coatings prepared from polyaniline/graphene composites” from 2012 by Chang et al in combination of knowledge acquired during a previous EU project, www.steelcoatproject.com concerning polyaniline for anti-corrosion coatings. The purpose of this master thesis is to optimize the synthesis of the, PAni, and GRM nanocomposite. Two different primary products of graphene oxides were investigated; water dispersed graphene oxide monolayer, GOW and water dispersed ammonia functionalized graphene oxide, AGO. These investigations were made to be able to confirm the presence of single sheets, the hybridizations of carbon and particle appearance and sheet size. A polyaniline/AGO nanocomposite made at SP before the initiation of this master thesis containing 20 wt% AGO was analyzed by Raman spectroscopy, SEM, TEM and AFM. The reaction at which the SP nanocomposite was made was reviewed to find improvements. Agglomeration occurs when AGO is added to the reaction mixture of aniline monomers and hydrochloric acid. Improvements were investigated by analyzing the pH during the synthesis and the usage of ultrasonication. The later tests were made with an AGO load of 1 wt% and was analyzed by SEM and Raman spectroscopy. The synthesis using an ultrasonication step showed the best dispersion according to the visual appearance and the intensity ratio between sp2 and sp3 bonds in the Raman spectra. Conclusion of this work is that the GRM products contain single sheets of the size of 1-7 µm for GOW and 4-10 µm for AGO, with a sp3/sp2 ratio of around 1. The PAni/AGO should be ultra-sonicated to obtain a well dispersed solution of AGO and aniline monomers before the synthesis is started by addition of the initiator.