Researchers at the Center for Multidimensional Carbon Materials (CMCM) (Ulsan, South Korea), located within the Institute for Basic Science (IBS), have recently demonstrated that a graphene coating can protect glass from corrosion.
Their published study, found in the American Chemical Society’s (Washington, DC) ACS Nano journal, can contribute to solving problems related to glass corrosion in several industries, according to the researchers.
Glass has a high degree of both corrosion and chemical resistance. For this reason, it is the primary packaging material to preserve medicines and chemicals, the researchers note. However, when exposed over time at high humidity and pH, some glass types can corrode.
Corroded glass loses its transparency, and its strength is also reduced. As a result, the corrosion of silicate glass, the most common and oldest form of glass, by water is a serious problem, the researchers say—especially for the pharmaceutical, environmental, and optical industries, and particularly those in hot and humid climates.
Although there are different types of glass, the researchers explain that ordinary glazing and containers are usually made of silicon dioxide (SiO2) and sodium oxide (Na2O), along with minor additives. Glass corrosion begins with the adsorption of water on the glass surface. Hydrogen ions from water then diffuse into the glass and exchange with the sodium ions present on the glass surface. The pH of the water near the glass surface increases, allowing the silicate structure to dissolve.
Scientists have examined how to better coat glass to protect it from damage. An ideal protective coating should be thin, transparent, and provide a good diffusion barrier to chemical attack, according to the researchers. Graphene possesses chemical inertness, thinness, and high transparency, thereby making it very promising as a coating material.
Moreover, owing to its excellent chemical barrier properties, a graphene coating can block helium atoms from penetrating through it. The use of graphene coating is also being explored as a protective layer for other materials requiring resistance to corrosion, oxidation, friction, bacterial infection, electromagnetic radiation, and more.
IBS scientists grew the graphene on copper and transferred either one or two atom-thick layers of graphene to both sides of rectangular pieces of glass. The effectiveness of the graphene coating was evaluated by water immersion testing and observing the differences between uncoated and coated glass.
After 120 days of immersion in water at 60 °C, the uncoated glass samples had significantly increased in surface roughness and defects while reducing in fracture strength. In contrast, both the single and double layer graphene-coated glasses had essentially no change in both fracture strength and surface roughness.
“The purpose of the study was to determine whether graphene grown by chemical vapor deposition on copper foils, a now established method, could be transferred onto glass, and protect the glass from corrosion,” says Prof. Rodney S. Ruoff, director of the CMCM and a professor at the Ulsan National Institute of Science and Technology (UNIST).
“Our study shows that even one atom-thick layer of graphene does the trick,” he adds. “In the future, when it is possible to produce larger and yet higher-quality graphene sheets and to optimize the transfer on glass, it seems reasonably likely that graphene coating on glass will be used on an industrial scale.”