MIT scientists
have designed a new sponge-like material that is lighter and about ten times
stronger than steel, by compressing and fusing flakes of graphene. In its 2D
form, graphene is thought to be the strongest of all known materials. However,
researchers, until now, have had a hard time translating that 2D strength into
useful 3D materials. The findings show that the crucial aspect of the new 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. Researchers at Massachusetts Institute of Technology in the US
analysed the material's behaviour down to the level of individual atoms within
the structure. They were able to produce a mathematical framework that very
closely matches experimental observations. Two-dimensional materials -
basically flat sheets that are just one atom in thickness but can be
indefinitely large in the other two dimensions - have exceptional strength as
well as unique electrical properties. However, due to their extraordinary
thinness, they are not very 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, producing a strong,
stable structure whose form resembled 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 remarkably strong. To do that, they
created a variety of 3D models and then 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, “one of our
samples has five per cent the density of steel, but 10 times the strength,”
said Zhao Qin, a CEE research scientist. Buehler 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. The research
appears in the journal Science Advances. -PTI
Source:DNA-10th January,2017
