IIT Delhi: Research shows thin graphene shields glass from mechanical, chemical damage under water

NEW DELHI: Ever noticed how something as simple as cleaning raindrops off your eyeglasses, wiping a windshield or removing spilled water from a glass tabletop can leave unsightly marks? These everyday scenarios reveal the vulnerability of glass, which, despite its transparency and functionality, is prone to surface damage during routine use.

Moving in the direction of addressing this challenge, the Indian Institute of Technology (IIT), Delhi has demonstrated that about a nanometre-thick graphene -- by virtue of its exceptional chemical shielding and mechanical strength -- can remarkably improve the durability of glass exposed to water.

A research paper, titled "Graphene Mitigates Nanoscale Tribochemical Wear of Silica Glass in Water", has been published in the "Nano, Micro, Small" journal.

According to Nitya Nand Gosvami, Professor at the Materials Science and Engineering Department, IIT-Delhi , surprisingly, the water surrounding us in the form of humidity or moisture makes things even worse. "For example, windshield wipers sweeping dusty glass during a rainy drive can create microscopic scratches as tiny dirt grinds against the surface. Similarly, cleaning a glass table or eyewear lens with a damp cloth may seem harmless, but water molecules can promote and seep into micro-scratches, wearing out the glass at a molecular level.

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Repeated tests were carried by researchers

"These water-driven processes, though often invisible, are a hidden enemy of glass, reducing its strength, lifespan and reliability," Gosvami told PTI. He explained that repeated scratch tests carried out by the researchers at the nanoscale revealed that just a few layers of graphene can transform fragile silica glass into a damage-resistant surface in water by preventing severe wear.

"Despite the ubiquitous use of glass, its simultaneous susceptibility toward scratch-induced defects and atmospheric hydration deteriorates its mechanical and chemical durability. Here, it is demonstrated that the deposition of a few-layer graphene provides unprecedented wear resistance to silica glass in aqueous conditions.

"To this extent, nanoscale scratch tests were carried out on graphene-glass surfaces via contact-mode atomic force microscopy with chemically inert and reactive tip," Gosvami said.

Practical solution to create ultra-durable glass coatings

The research highlights a simple yet practical solution for creating ultra-durable glass coatings, particularly for moisture-sensitive applications, such as smartphone screens, camera lenses, automotive windshields, solar panels and even optical instruments exposed to humid or wet environments. "Interestingly, zero wear was observed when scratched with both hard diamond and reactive silicon countersurfaces, despite the latter being aggressively corrosive to glass.

Molecular simulations reveal the secret behind graphene's effectiveness -- it prevents the chemical 'sticking' of glass to reactive bodies sliding in the presence of water. "This shielding ability of graphene protects the glass from combined physical and chemical damage," said N M Anoop Krishnan, Professor at IIT-Delhi's Civil Engineering Department.