The Superpowers of Super-Thin Materials


Researchers quickly set out to make all kinds of new and improved gadgets from it. Recently several companies released headphones with diaphragms — the vibrating membranes that produce sound in audio devices — made of graphene. Some paint manufacturers are adding graphene to their formulas to make longer-lasting coatings. Last October Huawei introduced the Mate 20 X, a large, powerful cellphone that uses graphene to help cool the processor. Samsung used graphene to develop a faster-charging battery, which may appear in phones in the near future.

Dr. Urban is working with 2-D materials to improve fuel cells, which have drawn interest as a clean propulsion system for green vehicles. Most fuel cells generate electricity from hydrogen, but even under high pressure hydrogen gas takes up several times more space than a comparable amount of gasoline, making it impractical to use in automobiles.

Instead, Dr. Urban is embedding hydrogen atoms in solids, which are much denser than gases. In March, he and his colleagues announced a new storage medium: tiny magnesium crystals wrapped in narrow strips called graphene nanoribbons. Hydrogen stored in this manner, they found, could provide nearly as much energy as the same volume of gasoline, while weighing much less.

Dr. Urban compared the process to baking chocolate chip cookies, where magnesium is the chocolate chip — the key part — because it holds the hydrogen. “We want a chocolate chip cookie with as many chocolate chips as possible,” he said, and graphene nanoribbon makes excellent cookie dough. The nanoribbon also helps hydrogen enter and exit the magnesium crystals quickly while boxing out oxygen, which competes with hydrogen for space in the crystals.

Dr. Urban peers into the super-thin realm at the Advanced Light Source, a domed laboratory with an expansive view of San Francisco and the neighboring bay. There, electrons are accelerated to near the speed of light, generating powerful X-rays that can be used to finely probe the atomic structure of materials.

At the A.L.S., Dr. Urban and his colleagues learned exactly how graphene wrapped around and bonded tightly to magnesium. Those bonds, they believe, are what make the composite material stable over long periods — an important trait for real-world use.



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