Characterization of Nanocomposite Graphene/polymer Films for Electrical Contact Applications

This paper presents a thin nanocomposite film, composed of graphene and of a polymer acting as a binder. The challenge was to realize a conducting, homogeneous and adherent film on a copper based material substrates (CuSn8) used for electrical contacts applications with the aim of reducing corrosion. The first step was to find the right formulation, the deposition process and the post-treatment for the composite. Flakes of graphene were mixed to two different types of high molecular weight polymers in ethanol. The films were deposited by dip-coating of the substrates in the solution; they were then grafted to the substrate by UV curing. Films between 100 nm to 300 nm thick could be deposited. Good adhesion of the film to the substrate was obtained with poly-4-vinylpyridine (P4VP) acting as a binder. The weight ratio of graphene/polymer was important for the homogeneity of the deposited films. The next step was to plate the samples with a nickel layer. Very thin nanometric nickel films were deposited on the graphene/polymer composite by an electroless nickel-boron process (NiB). The nickel nanofilm, a few tens of nanometres thick, was observed to be covering the graphene flakes embedded in the composite. Various techniques were used to characterize the samples: SEM, AFM, conducting AFM, Raman and 4 point sheet resistance measurements. Finally the samples were coated with 1.2 μm of electrolytic nickel and 0.4 μm of electrolytic gold. They were then exposed to nitric acid vapor (NAV) and hypochlorite bleach corrosion tests for several hours. The graphene composite layer was observed to hinder the pore and pitting corrosion on the samples. This process is very versatile and can find many applications in the field of corrosion protection.