Ever since its discovery ten years ago, scientists and engineers have expressed great expectations for the “wonder material” graphene. Just a single atom thick, these carbon sheets are not only the world’s thinnest material, but they are also the strongest. It therefore may not come as a complete surprise that scientists are now considering its use in body armor. After conducting miniature ballistic tests, graphene was found to perform twice as well as the material traditionally used in bulletproof vests, raising the possibility that it could be used as protection for police officers or members of the armed forces.
Graphene consists of a sheet of single carbon atoms arranged in a honeycomb structure. Alongside being incredibly strong, graphene also conducts heat and electricity remarkably well, resists rust and has excellent optical and mechanical properties. Graphene also achieves this impressive range of characteristics while being incredibly lightweight, which is why scientists began to wonder whether it would make a good addition to body armor.
Unfortunately, testing it out is not as simple as firing bullets through it and seeing what happens, because atom-thick material would be obliterated by such an impact. Examining its vigor therefore required a different tactic, so scientists from the University of Massachusetts-Amherst created a miniaturized ballistics test.
As described in the journal Science, the researchers used lasers to superheat gold filaments, which behaved like gunpowder and fired tiny silica spheres, or “microbullets,” at sheets of graphene ranging from 10 to 100 nanometers in thickness.
By comparing the kinetic energy of the spheres before and after they penetrated the sheets, they found that graphene dissipates this energy by warping into a cone shape at the site of impact, and then cracking outward. While these cracks represent a weakness, the material still performed twice as well as Kevlar, the lightweight fiber used in body armor. Furthermore, it absorbed between 8 and 10 times the impacts that steel is able to withstand.
In the future, scientists might be able to overcome the cracking problem by combining it with other materials to generate a composite, the researchers said.
Interestingly, another paper came out this week in Nature which revealed a previously unknown property of graphene: it is permeable to protons. This raises the possibility that it could be used to improve fuel-cell technology, or even to harvest hydrogen from the atmosphere.
Hydrogen fuel cells create electrical energy through a reaction between hydrogen and oxygen. They rely on semi-permeable membranes that allow the passage of protons but block other particles. Existing materials, however, let some hydrogen fuel leak through, which reduces efficiency of the system. But graphene seems to be impermeable to everything but protons, suggesting it could be an ideal solution to the problem.
Furthermore, this newly identified property could mean that one day, graphene could be used as a sieve to extract hydrogen from air, meaning we could pump fuel from the atmosphere and generate electricity from it. While that prospect is exciting, it is purely speculation at this stage.