(294c) Controlled Assembly of Graphene Sheets and Carbon Nanospheres for Electrically Conductive Barrier Coating Applications

Conductive composite coatings prepared by conventional techniques (spray, brush, curtain, etc.) typically contain high loading levels (>5%) of electrically conductive filler particles mixed with a polymeric matrix material. Connectivity between dispersed filler particles is the key to the electrical conductivity in these coatings. However, optimization of connectivity through the random surface interactions present in conventional composite formulations is difficult. In the present investigation, we employ Layer by Layer (LBL) assembly of graphene sheets in the form of graphite platelets as well as amorphous carbon nanospheres (both pure and heterogeneous systems) to prepare well defined and controllable nanostructured coatings with > 99% of the conductive filler yet having thicknesses of 100-300 nm. Despite low coating loading (thickness) and contact resistance (~ 2 mΩ-cm²), electrostatic interactions between nanoparticles may be optimized through systematic alteration of the suspending media to achieve sufficiently high nanoparticle packing densities in the coatings for gas barrier applications. Data is presented to demonstrate the correlation between nanoparticle zeta potential in the suspending medium, coating packing density on gold and stainless steel as observed using AFM and high resolution SEM, and the effective diffusion coefficient of oxygen obtained through electrochemical rotating disk electrode (RDE) experiments on platinum. Finally, LBL assembled carbon nanoparticle coatings are shown to inhibit stainless steel corrosion in acidic media.