Oxidation Resistance of Fe and Cu Foils Coated with Reduced Graphene Oxide Sheets

Abstract

The size and the physical properties of graphene oxide sheets were controlled by changing the oxidation temperature of graphite and graphene oxide sheet were applied for protection of metal surface as a diffusion barrier layer. Graphite oxide (GO) samples were prepared at different oxidation temperatures of 20 oC, 27 oC, and 35 oC using a modified Hummers’ method. The C/O ratio and the average size of the GO sheets varied according to the oxidation temperature: 1.26 and 12.4 μm at 20 oC, 1.24 and 10.5 μm at 27 oC, and 1.18 and 8.5 μm at 35 oC. This indicates that the C/O ratio and the average size of the graphene oxide sheets respectively increase as the oxidation temperature decreases. Moreover, it was observed that the surface charge and optical property of the graphene oxide sheets could be tuned by changing the temperature. This study demonstrates tunability of the physical properties of graphene oxide sheets and shows that the properties depend on functional groups generated during the oxidation process. The protection of metals such as Fe and Cu, which are widely used in industry, is of great importance because of necessity to preserve their surface properties. Traditional protection methods including organic layer, paints, polymer deposition and formation of oxide layer may have some problems such as change of physical property and surface deformation. Recently, oxidation resistance of graphene-coated metal has been reported. However, they used CVD-grown graphene which has some limits: difficulty in reproducible growth of graphene with large area and complicated process such as high temperature and gas. In this study, we demonstrate possibility of oxidation resistance of Cu and Fe coated with reduced graphene oxide (RGO) sheets. The RGO thin films on SiO2 substrate by layer-by-layer assembly was transferred to Cu and Fe substrate. Then, we checked the oxidation resistance of the RGO-coated metal substrates in the condition of 200 oC in air. The substrates were characterized by Raman spectroscopy and scanning electron microscopy. This study affords an advantage of a simple solution process which enables coating of large area.