In the search for a better material for bullet-proof vests, researchers are turning to graphene, which they say works twice as well as the high-tech fabrics currently utilized in body armor for police and soldiers.
Researchers conducted miniature ballistic tests in which they fired tiny spheres of silicon at graphene -- sheets of single carbon atoms in a honeycomb lattice -- and found the material can be stronger than steel for absorbing impacts.
Lasers were used to fire the tiny "microbullets" against graphene sheets between 10 and 100 layers thick, engineers at the University of Massachusetts in Amherst reported in the journal Science.
The silicon spheres were fired at about at 3,000 meters per second, about a third of the speed of a typical rifle bullet.
Examination with an electron microscope showed the graphene sheets absorbed the impacts by deforming into a cone shape and then cracking outward in multiple directions in a radial pattern.
That cracking, which can result in a wider impact hole, is a possible weakness of single-layer graphene, research leader Jae-Hwang Lee says, but even so graphene is twice as effective at absorbing impacts as Kevlar, the current material of choice for body armor, and 10 times more effective than steel.
Graphene sheets, currently too brittle to be used to create a solid material, could be built up in multiple layers or incorporated in a composite structure with other materials to prevent the cracks from spreading, the researchers say.
Energy waves have been found to travel through graphene three times as fast as they do in steel, meaning graphene material well away from the impact site can help quickly absorb and then dissipate the energy of a projectile, they point out.
The research is the latest to investigate the properties of graphene, which had been theorized for decades but first produced in 2003 in the laboratory of researchers Andre Geim and Konstantin Novoselov at Manchester University in Britain.
Their work brought them a Nobel Prize for Physics in 2010.
Ongoing research has targeted graphene, which can conduct electricity and heat extremely efficiently, for uses in the fields of electronics, lightweight composite materials, biological engineering, energy storage and a number of other possibilities.
Lee points out that his team's microbullet technology can be used in studies of the performance of other high-tech materials under extreme conditions.