Famously durable, diamond is the hardest natural substance that occurs in any significant abundance on Earth. Yet according to a new study, on the nanoscale—a scale size of just billionths of a meter—diamond can, in fact, be bent and deformed. This discovery could pave the way to developing new nanotechnologies for a host of applications ranging from energy storage to sensing to radiation shielding. See also: Diamond; Energy storage; Nanotechnology
A research team conducted experiments with single crystals of diamond, known as either diamond nanoneedles or diamond nanopillars, measuring about 20 nm in length. When exposed to an electric field from a scanning electron microscope, the nanoneedles could be induced via electrostatic forces to lose their linear shape, even able to bend at their middle as far as 90 degrees while preserving the integrity of the crystal structure. Researchers observed both elastic deformation—a temporary distortion of shape that reverses when an external force is no longer applied—and plastic deformation, or permanent shape distortion after a force is withdrawn. See also: Crystal; Crystal structure; Electric field; Electrostatics; Plasticity; Scanning electron microscope
According to the study, the molecular mechanism enabling this unprecedented shape change in diamond is the formation of a new form of carbon, dubbed 08-carbon. As a chemical element, carbon is extraordinary due to the number of chemical bonds it can form, including with itself. A slight change in pure carbon's crystal structure can result in materials with vastly different properties, such as diamond, charcoal, graphite, and graphene—all among the best-known carbon allotropes, or different physical forms that an element can take. The newly documented allotrope, 08-carbon, is not rigid in the same way as diamond. The allotrope in the study appeared within regions of nanopillars under strain, where diamond chemical bonds broke apart in a zipper-like fashion while the bonds upstream and downstream remained locked, ultimately causing straight nanopillars to bend at specific locations. See also: Charcoal; Chemical bonding