Carbyne — essentially a chain of carbon atoms held together by either double or alternating single and triple atomic bonds — will be the strongest material (tensile strength) in the world if anyone ever works out a means of producing it in bulk, new research from Rice University has found.
In addition to carbyne’s incredible strength, which is double that of graphene, the material possesses a wide-range of “remarkable” and useful qualities, according to the researchers — especially when formed into nanorods and nanoropes.
Carbyne has actually been around for some time now — an approximation of it was first synthesized in the USSR in 1960. However, until this research, there really wasn’t that much known about it — though, it has been detected since then in interstellar dust and compressed graphite.
So, to address this lack of knowledge, Rice University theoretical physicist Boris Yakobson, along with his research group, set out to create a “portrait” of the material “with computer models using first-principle rules to determine the energetic interactions of atoms.”
Some of the key findings are detailed below:
- Carbyne’s tensile strength — the ability to withstand stretching — surpasses “that of any other known material” and is double that of graphene. (For some perspective, it would take an elephant standing on a pencil to break through a single sheet of graphene.)
- It has 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.
- If outfitted with molecular handles at the ends, it can also be twisted to alter its band gap. With a 90-degree end-to-end rotation, it becomes a magnetic semiconductor.
- Carbyne chains can take on side molecules that may make the chains suitable for energy storage.
- The material is stable at room temperature, largely resisting crosslinks with nearby chains.
That’s a rather impressive and interesting array of characteristics, Yakobson explains: “You could look at it as an ultimately thin graphene ribbon, reduced to just one atom, or an ultimately thin nanotube. It could be useful for nanomechanical systems, in spintronic devices, as sensors, as strong and light materials for mechanical applications or for energy storage, etc.”
And, interestingly, carbyne may be the highest energy state possible for stable carbon: “People usually look for what is called the ‘ground state,’ the lowest possible energy configuration for atoms. 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.”
In something that was a bit of a surprise to the researchers, it turns out that the band gap in carbyne is very sensitive to twisting. A welcome surprise though, as Artyukhov notes: “It will be useful as a sensor for torsion or magnetic fields, if you can find a way to attach it to something that will make it twist. We didn’t look for this, specifically; it came up as a side product.”
Another important finding was the discovery of “the energy barrier that keeps atoms on adjacent carbyne chains from collapsing into each other.” Artyukhov explains: “When you’re talking about theoretical material, you always need to be careful to see if it will react with itself. This has never really been investigated for carbyne.”
Previous research had indicated that carbyne wasn’t stable and would instead quickly transform into graphite and/or soot. That apparently isn’t the reality though, instead “carbon atoms on separate strings might overcome the barrier in one spot, but the rods’ stiffness would prevent them from coming together in a second location, at least at room temperature.”
“They would look like butterfly wings,” Artyukhov explains. Yakobson continues: “Bundles might stick to each other, but they wouldn’t collapse completely. That could make for a highly porous, random net that may be good for adsorption.”
The researchers are planning to continue investigating the material — specifically looking to develop a more in-depth understanding of its conductivity — but, they’re also looking to begin investigations into the one-dimensional forms of elements other than carbon. “We’ve talked about going through different elements in the periodic table to see if some of them can form one-dimensional chains,” Yakobson states.
The research was financially supported by both the Air Force Office of Scientific Research and the Welch Foundation. The National Science Foundation-supported DaVinCI supercomputer — administered by Rice’s Ken Kennedy Institute for Information Technology — performed the calculations for the research.
The new findings were just detailed in a paper published in the American Chemical Society journal ACS Nano.
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