MIT researchers design a material 10 times as strong as steel but much lighter

A team of researchers at MIT claims to have designed one of the strongest lightweight materials known by compressing and fusing flakes of graphene. The material, a sponge-like configuration with a density of 5%, is said to have a strength 10 times that of steel.

In its two-dimensional form, graphene is thought to be the strongest of all known materials. But researchers have struggled to translate that two-dimensional strength into useful three-dimensional materials.

These findings show that the crucial aspect of the 3D forms has more to do with their unusual geometrical configuration than with the material itself, which suggests that similar strong, lightweight materials could be made from a variety of materials by creating similar geometric features.

The team was able to compress small flakes of graphene using a combination of heat and pressure. This process produced a strong, stable structure with an enormous surface area in proportion to its volume.

“Once we created these 3D structures, we wanted to see what’s the limit — what’s the strongest possible material we can produce,” said Zhao Qin, a research scientist in MIT’s Department of Civil and Environmental Engineering (CEE).

To do that, the researchers created a variety of 3D models which they subjected to various tests and computational simulations which mimic the loading conditions in the tensile and compression tests performed in a tensile loading machine.

Markus Buehler, the head of CEE, said that what happens to their 3D graphene material, which is composed of curved surfaces under deformation, resembles what would happen with sheets of paper. Paper has little strength along its length and width, and can be easily crumpled. But when rolled into a tube, for example, the strength along the length of the tube is greater. Similarly, the geometric arrangement of the graphene flakes after treatment naturally forms a very strong configuration.

These configurations were made using a high-resolution, multimaterial 3D printer. They were mechanically tested for their tensile and compressive properties, and their mechanical response under loading was simulated using theoretical models. The results from the experiments and simulations matched accurately.

For actual synthesis, according to the researchers, one possibility is to use polymer or metal particles as templates, coat them with graphene by chemical vapour deposit before heat and pressure treatments, and then chemically or physically remove the polymer or metal phases to leave 3D graphene in the gyroid form.

The same geometry could even be applied to large-scale structural materials. For example, concrete for structures such as bridges might be made with this porous geometry, providing comparable strength with a fraction of the weight. This approach would have the additional benefit of providing good insulation because of the large amount of enclosed airspace within it.

Because the shape is riddled with very tiny pore spaces, the material might also find application in some filtration systems, for either water or chemical processing.

“You can replace the material itself with anything,” Buehler says. “The geometry is the dominant factor. It’s something that has the potential to transfer to many things.”

Author
Tom Austin-Morgan

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