TechFront Research and Development in Manufacturing and Technology
Carbyne Chains Hold Promise for Creating Stronger Nanomaterials
C
arbyne may turn out to be the strongest of a new class of microscopic materials ever, if scientists can determine an effective way to produce it in bulk. Researchers at Rice University (Houston) have studied carbyne nanorods or nanoropes that could have a host of remarkable and useful properties, which are described by Rice University theoretical physicist Boris Yakobson and his group in a paper published in the American Chemical Society journal ACS Nano.
Carbyne, a chain of carbon atoms held together by either double or alternating single and triple atomic bonds, is a true one-dimensional material, unlike atom-thin sheets of gra- phene that have a top and a bottom or hollow nanotubes that have an inside and outside. In calculations by Yakobson and his group, carbyne’s tensile strength—the ability to withstand stretching—surpasses “that of any other known material” with twice the tensile stiffness of graphene and carbon nanotubes, and nearly three times that of diamond.
Stretching carbyne as little as 10% alters its electronic band gap significantly, the Rice researchers noted. If outfitted with molecular handles at the ends, it can also be twisted to alter its band gap. With a 90° end-to-end rotation, it becomes a magnetic semiconductor. Carbyne chains also can take on side molecules that may make the chains suitable for energy storage, according to the researchers, and it is stable at room temperature, largely resisting crosslinks with nearby chains. That’s a remarkable set of qualities for a simple string of carbon atoms, said Yakobson, Rice’s Karl F. Hasselmann Professor of Mechanical Engineering and Materials Science, a professor of chemistry and a member of the Richard E. Smalley Institute for Nanoscale Science and Technology. “You could look at it as an ultimately thin graphene ribbon, reduced to just one atom, or an ultimately thin nanotube,” Yakobson said.
The material could be useful for nanomechanical systems, in spintronic devices, as sensors, as strong and light materials for mechanical applications or for energy storage. “Regardless
of the applications,” Yakobson noted, “academically, it’s very exciting to know the strongest possible assembly of atoms.” Based on the calculations, carbyne might be the highest energy state for stable carbon, he said. “People usually look for what is called the ‘ground state,’ the lowest possible energy configuration for atoms,” Yakobson said. “For carbon, that would be graphite, followed by diamond, then nanotubes, then fullerenes. But nobody asks about the highest energy configuration. We think this may be it, a stable structure at the highest energy possible.”
Rice University researchers determined from first-principle calculations that carbyne would be the strongest mate- rial yet discovered. The carbon-atom chains would be difficult to make but would be twice as strong as 2D graphene sheets.
Scientific theories about carbyne first appeared in the 19th century, and an approximation of the material was first synthesized in the USSR in 1960. Carbyne has since been
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Photo courtesy Vasilii Artyukhov, Rice University
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