Sameh Tawfick from the University of Illinois at Urbana-Champaign. Photo: University of Illinois Department of Mechanical Science and Engineering.Gilding is the process of coating intricate artifacts with precious metals. The ancient Egyptians and Chinese used gilding to coat their sculptures with thin metal films – and these golden sculptures have resisted corrosion, wear and environmental degradation for thousands of years. The middle and outer coffins of Tutankhamun, for instance, are gold-leaf gilded, as are many other ancient treasures.
Inspired by this ancient process, Sameh Tawfick, an assistant professor of mechanical science and engineering at the University of Illinois at Urbana-Champaign, and his team experimented with adding a single layer of graphene on top of metal leaves being used for gilding. They found that this doubled the protective quality of gilding against wear and tear.
Tawfick and his team report their findings in a paper in Advanced Functional Materials. The researchers coated thin metal leaves of palladium with the single layers of graphene.
Metal leaves, or foils, offer many advantages as a scalable coating material, including their commercial availability in large rolls and their comparatively low price. By bonding a single layer of graphene to the leaves, Tawfick and his team demonstrated unexpected benefits, including enhanced mechanical resistance. Their work suggests exciting opportunities for protective coating applications on large structures like buildings or ship hulls, metal surfaces of consumer electronics, and small precious artifacts or jewelry.
"Adding one more layer of graphene atoms onto the palladium made it twice as resistant to indents than the bare leaves alone," said Tawfick. "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."
Additionally, the team developed a new technology to grow high-quality graphene directly on the surface of 150nm-thin palladium leaves – in just 30 seconds. Using a process called chemical vapor deposition, in which the metal leaf is processed in a furnace at 1100°C, 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 dewetting," said Kaihao Zhang, a PhD candidate in mechanical science and engineering and lead author of the study. "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."
This story is adapted from material from the University of Illinois at Urbana-Champaign, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.