A team of scientists from Rice University and the Georgia Institute of Technology tested small pieces of "bilayer" graphene, two single-atom-thick sheets of pure carbon resting one atop the other,by making tiny cracks in them with focused beams of ions. They then pulled the graphene, to see how fast the cracks expanded until the material broke.
Result? It can crack.
Graphene the miracle material known for its high electric conductivity and it's hundreds of times strength than steel has an Achilles heel. Tests of real-world samples of graphene show that while the carbon material is possibly the strongest material produced today, it's. Our miracle material is also as brittle as ordinary ceramic.
"It's very sensitive to [the] presence of [a] crack. In steel if you have a crack, there, it's not so dangerous. Steel has a huge resistance to crack extension. Graphene is more like window glass," said Ting Zhu, an associate professor of mechanical engineering at Georgia Tech and one of the authors of the study.
Zhu, working with Jun Lou at Rice, found that graphene with cracks is 10 times more prone to breakage than steel, and closer in fracture toughness to aluminum oxide or silicon carbide-based ceramics.
Perfect graphene can take about 100 Gigapascals (14 million pounds per square inch) of force before it breaks. But the imperfect graphene the researchers made can withstand only a tiny fraction of that, about 4 Megapascals (580 pounds per square inch).
The experiments aren't just important for the study of graphene. Other materials that can take on a two-dimensional structure might behave in a similar way, and as such the new research, detailed today (April 29) in the journal Nature Communications, might offer important insights.
"This kind of modeling could be applied to study many other 2D materials, such as molybdenum disfulfide or boron nitride," Zhu said.
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