Graphene
The theory of graphene was first explored by Wallace in 1947 as a starting point for understanding the electronic properties of 3D graphite. The emergent massless Dirac equation was first pointed out by Semenoff, DiVincenzo and Mele. The earliest TEM images of few-layer graphite were published by Ruess and Vogt in 1948. An early, detailed study on few-layer graphite dates to 1962 when Boehm and colleagues reported producing monolayer flakes of reduced graphene oxide. Efforts to make thin films of graphite by mechanical exfoliation started in 1990, but nothing thinner than 50 to 100 layers was produced before 2004. Initial attempts to make atomically thin graphitic films employed exfoliation techniques similar to the drawing method. Multilayer samples down to 10 nm in thickness were obtained.
Bulletproof vest
In late 2014, researchers began studying and testing graphene as a material for use in body armor. Graphene is manufactured from carbon and is the thinnest, strongest, and most conductive material on the planet. Taking the form of hexagonally arranged atoms, its tensile strength is known to be 200 times greater than steel, but studies from Rice University have revealed it is also 10 times better than steel at dissipating energy, an ability that had previously not been thoroughly explored. To test its properties, the University of Massachusetts stacked together graphene sheets only a single carbon atom thick, creating layers ranging in thickness from 10 nanometers to 100 nanometers from 300 layers. Microscopic spherical silica "bullets" were fired at the sheets at speeds of up to 3 km (1.9 mi) per second, almost nine times the speed of sound. Upon impact, the projectiles deformed into a cone shape around the graphene before ultimately breaking through. In the three nanoseconds it held together however, the transferred energy traveled through the material at a speed of 22.2 km (13.8 mi) per second, faster than any other known material. If the impact stress can be spread out over a large enough area that the cone moves out at an appreciable velocity compared with the velocity of the projectile, stress will not be localized under where it hit. Although a wide impact hole opened up, a composite mixture of graphene and other materials could be made to create a new, revolutionary armor solution.