The graphene material is a two-dimensional modification of carbon one atom thick with a hexagonal crystal lattice. Scientists are very interested in this material, because it has a number of properties that make it almost universal and applicable in any area of production. And this material is theoretically considered the most durable substance in the world.
Materials scientists from Rice University in Houston (USA) have found a way to make graphene significantly stronger than its original state. How? Thanks to the carbon nanotubes included in its structure. The researchers also report that they were able to achieve in three-dimensional structures based on graphene levels of strength up to 10 times higher than the original value. Scientists shared the results of the work done in the ACS Nano magazine.
“We have demonstrated the ability to grow graphene with integrated nanotubes. We call this graphene reinforcing graphene. But unlike reinforcing concrete, which uses steel rods to strengthen the structure, we use carbon nanotubes in reinforcing graphene, ”explains study head James Tour, professor of materials science and nanoengineering at Rice University.
Despite its strength, 100 times higher than that of steel, explains Professor Tur, structural defects at the junctions of the crystal lattice, as well as its thinness, can reduce the fracture toughness of the material. In practice, this means that graphene is unable to reach its theoretical maximum strength. However, the integration of carbon nanotubes into the graphene structure during its production makes it possible to enhance it and reduce the likelihood of cracks in its crystal lattice.
The production of reinforcing graphene itself is as follows. First, scientists created nanotubes by wrapping a monatomic layer of carbon around a copper substrate, and only then proceeded to grow graphene around the created carbon nanotubes using the process of plasma-chemical vapor deposition.
“This led to the emergence of a chemical covalent bond between the graphene layer and the nanotubes,” says Thor.
From a practical point of view, the new process for the production of structurally reinforced graphene does not endow the material with new properties, but it significantly increases the possibility of its application in real conditions, since its real efficiency is most often limited only by weak links in its structure.
“This allows you to do things with graphene that were originally intended, but were not possible due to possible defects,” says Thor.
In previous tests, scientists from Rice University found that the natural fracture toughness of ordinary graphene is 4 megapascals. Inspection of reinforcing graphene on average showed fracture toughness at the level of 10.7 megapascals. As noted above, the difference becomes even more obvious when using graphene-based 3D structures.
Next, scientists want to think about how to scale the production process, making their discovery really practical and applicable in real conditions.
“We want to achieve scalability in manufacturing so that this reinforced graphene can be produced in large volumes. It would really change a lot of things. This is what we are striving for, ”added Tur.