Material 10 times stronger than graphene overturns 100-year theory


Researchers at Rice University, USA, have discovered a material stronger than graphene. Hexagonal boron nitride has physical characteristics similar to its brother in the periodic table, but it is more resistant to cracking when subjected to torque and pressure situations.

Both graphene and boron nitride have hexagonal lattices of atoms. In the case of graphene, all these atoms are carbon, unlike boron nitride, where each hexagon contains three boron atoms and three nitrogen atoms.

“We measured the fracture resistance of graphene seven years ago and, in fact, it’s not very strong in that regard. If there is a simple crack in the network, a small load will be enough to break this material,” explains Professor Jun Lou , responsible for the study.

measuring forces

While graphene has a strength of approximately 130 gigapascals (1 pascal equals a force of 1 Newton applied uniformly over a one square meter surface) and an elasticity of 1 terapascal, hexagonal boron nitride has 100 gigapascals of hardness and 0.8 of malleability.

Even at these lower indices, when the researchers did the first laboratory tests, they found that the strength of hexagonal boron nitride is about ten times greater than that of graphene.

The finding goes against the fundamental description of fracture mechanics, first presented by the English engineer Alan Arnold Griffith, in 1921. The theory states that cracks propagate when the stress placed on a material is greater than the force holding it. united.

Despite being physically identical, the two materials have a completely different behavior when it comes to cracking. In graphene, a crack tends to develop zigzag movements straight through the symmetrical hexagonal structure, always from top to bottom.

Boron nitride, on the other hand, has a slight asymmetry in its hexagonal structure because of the stress contrast between boron and nitrogen. This causes the cracks to travel bifurcated paths from one end to the other and this is what makes the material much stronger.

“If the crack is branched, it means it’s spinning. If you have this spinning crack, it basically takes additional energy to drive the crack. With that, you can harden the material, making the crack propagation much more difficult,” he says. Professor Lou.

varied applications

In the future, hexagonal boron nitride could replace graphene in the development of more flexible and efficient 2D materials. Its heat resistance and chemical stability properties are critical for electronic applications that demand precision and low power consumption.

As it is more resistant and malleable than graphene, hexagonal boron nitride can be used in the manufacture of electronic fabrics, smart adhesives and even highly complex medical implants.

The researchers hope to be able to prove the advantages of the two-dimensional material away from the laboratory, using boron nitride in different devices. The idea is to make it a viable and more efficient alternative to graphene for large-scale application and production.

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