Researchers at the Massachusetts Institute of Technology (MIT) have produced one of the strongest and lightest materials known by compressing and fusing graphene flakes, a two-dimensional form of carbon. Its calculated density was only 5% of the density of steel with a tenfold increase in its strength. The corresponding work was published in the journal Science Advances.
In its original form, graphene is considered the strongest of all known materials, and its theoretical studies began in the late forties of the last century. This is the world's first two-dimensional crystal obtained by Andrey Geim and Konstantin Novoselov in 2004 from the thinnest graphite films on an oxidized silicon substrate. For this achievement, they were awarded the Nobel Prize in Physics six years later.
Since the inception of graphene, methods for its production on an industrial scale have been developed. Some progress has already been achieved in this, however, it has not yet been possible to successfully transform it into an effective three-dimensional form - important properties of this exceptional material were lost, and its strength was several orders of magnitude lower than predicted.
To solve this problem, engineers at MIT focused on the required geometric configuration of bulk graphene. They analyzed its behavior down to the atomic level, and then used the data obtained to create a mathematical model and computer simulation. The final conclusions were exactly in line with experimental observations, which were initially carried out with models of other materials magnified a thousand times, printed on a high-resolution 3D printer.
According to Markus Buehler, head of civil and environmental engineering at MIT, 2D materials are usually not very useful for creating 3D objects that can be used in the construction of buildings. But computer modeling made it possible to overcome this problem, and geometry became the determining factor for success.
As a result, the researchers were able to create a strong and stable porous material by compressing and heating small graphene flakes. Its structure, reminiscent of some corals and microscopic diatoms, has a huge surface area in relation to volume. It is known as a gyroid, a continuous repeating shape with a triple periodic minimum surface, described by Alan Schoen of NASA in 1970.
"The results show that the crucial aspect of the new three-dimensional shapes has more to do with their unusual geometric configuration than with the material itself," noted at MIT.
According to the institute's engineers, such geometry can be applied even to large-scale structural materials in construction, such as concrete. And this porous structure will not only provide increased strength, but also good thermal insulation thanks to the air inside it.
“You can either use real graphene as a material, or apply the geometry we discovered in combination with other materials, such as polymers or metals,” concluded Markus Buehler.
