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Researchers at the Center for Multidimensional CarbonMaterials (CMCM), within the Institute for Basic Science (IBS) have demonstrated howgraphene coating protects glass fromcorrosion. Their research can contribute to solving problems related to glass corrosion in several industries. Glass has a high degree of both corrosion

and chemical resistance. For this reason it is a primary packagingmaterial to preserve medicines and chemicals. However, over time at high humidity and pH, some glass types corrode. Corroded glass loses its transparency and its strength is reduced. As a result, the corrosion bywater of silicate glass, themost common and oldest formof glass, is a serious problem, especially for the pharmaceutical, environmental and optical industries, and in particular in hot and humid climates. Although there are different types of glass, ordinary glazing and containers are

made of silicon dioxide (Si02), sodiumoxide (Na20) alongwithminor additives. Glass corrosion beginswith the adsorption of

water on the glass surface. Hydrogen ions fromwater then diffuse into the glass and exchangewith the sodiumions present on the glass surface. The pH of thewater near the glass surface increases, allowing the silicate structure to dissolve. Scientists have been looking at howto

coat glass to protect it fromdamage. An ideal protective coating should be thin, transparent, and provide a good diffusion barrier to chemical attack. Graphenewith its chemical inertness, thinness, and high transparencymakes it very promising as a coatingmaterial.Moreover, owing to its excellent chemical barrier properties, it blocks heliumatoms frompenetrating

 An example of a glass showing cracking and opacity due to corrosion

through it. The use of graphene coating is being explored as a protective layer for othermaterials requiring resistance to corrosion, oxidation, friction, bacterial infection, electromagnetic radiation, etc.

IBS scientists grewgraphene on copper  Corrosion mechanism on the glass surface

using a technique previously invented by Prof Rodney S Ruoff, director of the CMCM and Professor at the Ulsan National Institute of Science and Technology (UNIST), and transferred either one or two atom-thick layers of graphene onto both sides of rectangular pieces of glass. The effectiveness of the graphene coatingwas evaluated bywater immersion testing and observing the differences between uncoated and coated glass. After 120 days of immersion inwater at 60°C, uncoated glass samples had significantly increased in surface roughness and defects, and reduced 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 studywas to

 Graphene coatings protect glass from corrosion as shown in the atomic force microscopy images on the right. On uncoated glass (top right), the surface roughness increases after immersion in water for 120 days. In contrast, glass plates coated with graphene films were much more stable and the increase in roughness was negligible after immersion in water for 120 days

8 /// Environmental Engineering /// December 2016

determinewhether graphene grown by chemical vapour deposition on copper foils, a nowestablishedmethod, could be transferred onto glass, and protect the glass fromcorrosion. Our study shows that even one atom-thick layer of graphene does the trick,” explains Ruoff. “In the future,when it is possible to produce larger and yet higher- quality graphene sheets and to optimise the transfer on glass, it seems reasonably likely that graphene coating on glasswill be used on an industrial scale.”


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