University of Illinois at Urbana–Champaign (Champaign, Illinois, USA) engineers say they have doubled the protective quality of gilding against wear by adding one layer of graphene.
In their study, the researchers coated thin metal leaves of palladium with the graphene. Metal leaves, or foils, offer many advantages as a scalable coating material, the researchers explain, including their commercial availability in large rolls and their comparatively low price. By bonding a single layer of graphene to the leaves, the team says it demonstrated unexpected benefits, including enhanced mechanical resistance.
“Adding one more layer of graphene atoms onto the palladium made it twice as resistant to indents than the bare leaves alone,” says Sameh Tawfick, an assistant professor in mechanical science and engineering. “It’s also very attractive from a cost perspective. The amount of graphene needed to cover the gilded structures of the Carbide & Carbon Building in Chicago, for example, would be the size of the head of a pin.”
The team also developed a new technology to grow graphene directly on the surface of 150-nm palladium leaves in just 30 s. Using chemical vapor deposition, in which the metal leaf is processed in a 1,100 °C furnace, the bare palladium leaf acts as a catalyst, allowing the gases to react quickly.
“Chemical vapor deposition of graphene requires a very high temperature, which could melt the leaves, or cause them to bead up by a process called solid state de-wetting,” says Kaihao Zhang, a doctoral candidate and the study’s lead author. “The process we developed deposits the graphene quickly enough to avoid high-temperature degradation, it’s scalable, and it produces graphene of very high quality.”
Source: University of Illinois at Urbana–Champaign, mechanical.illinois.edu.