Evaluation of graphene transparent coating on copper for color and oxidation control at low temperatures

Abstract

In this paper, the ability to preserve copper color was investigated by using graphene thin film coating against oxidation at 200 °C. For this purpose, graphene nano-coating was applied to the copper substrate by using chemical vapor deposition (CVD) process. Raman spectroscopy was used for the detection of the coatings. Structural investigation of the coating was performed before and after oxidation tests using optical and scanning electron microscopes. Color changes due to the formation of copper oxides were calculated using the CIE–L*a*b* color space defined by the Commission Internationale de l'Éclairage (CIE). Furthermore, the reflectance was evaluated in the UV–visible spectrum range. The results revealed that the graphene coated copper had a higher L* than the untreated copper due to the removal of oxide layer during graphene synthesis. The color change (∆E) caused by oxidation at 200 °C, in the graphene coated copper was negligible (∆E = 2.88) after 2 h, and its value was below 5 after 4 h. However, the color change on the bare copper surface was significant (∆E = 26.87) after 15 min of oxidation. The results of the present research show that the graphene coating is effective in protecting copper color. Moreover, since graphene oxidation extends from defects and grain boundaries, synthesis technique plays an important role in protecting copper against oxidation and thus preserving its color.