Engineering news
Researchers at the Massachusetts Institute of Technology (MIT) have designed a strong and lightweight material, by compressing and fusing flakes of graphene, a two-dimensional form of carbon.
The material has a sponge-like configuration with a density of 5% of steel, and can have a strength 10 times that of steel, according to the researchers. The material could be used for a variety of applications, such as filtration systems for water or chemical processing, or concrete for bridge structures, providing comparable strength with a fraction of the weight and good insulation because of the large amount of enclosed airspace within it.
Two-dimensional materials are flat sheets that are just one atom in thickness, but can be indefinitely large in the other dimensions and have high strength as well as distinctive electrical properties. However, because of their thinness, they have not been useful for making 3D materials that could be used in vehicles, buildings, or devices.
The team was able to compress small flakes of graphene using a combination of heat and pressure. This process produced a strong, stable structure whose form resembles that of some corals and microscopic creatures called diatoms. These shapes, which have an enormous surface area in proportion to their volume, proved to be very strong.
The team created a variety of 3D models using a 3D printer and subjected them to various tests. In computational simulations, which mimic the loading conditions in the tensile and compression tests performed in a tensile loading machine, a sample had 5% the density of steel but 10 times the strength, according to the team.
The 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 up. However, when made into certain shapes, for example rolled into a tube, suddenly the strength along the length of the tube is much greater and can support substantial weight. Similarly, the geometric arrangement of the graphene flakes after treatment naturally forms a very strong configuration.
The unusual geometry is too complex for conventional manufacturing methods. For actual synthesis, polymer or metal particles could be used as templates, and then coated with graphene by chemical vapor deposit before heat and pressure treatments. The polymer or metal would then be removed to get the 3D graphene.
The crucial aspect of the 3D forms is their unusual geometrical configuration rather than the material itself, which suggests that similar strong, lightweight materials could be made from a variety of materials.
Markus Buehler, the head of MIT’s department of civil and environmental engineering, said: “You can replace the material itself with anything. The geometry is the dominant factor. It’s something that has the potential to transfer to many things.”
The research was published in the journal
Science Advances.