In developing nano-composite materials, nanotubes and nanowires are expected to greatly improve the properties of the composites. Silicon carbide nanowires have been regarded as an excellent reinforcement for composites due to the high intrinsic strength of the materials. However, the silicon carbide nanowires have a smooth surface and are easily pulled out when the composites break because of the weak adhesion between the nanowires and the matrix. Therefore, we need to fabricate a contoured surface of the silicon carbide nanowires in order to improve the adhesion.

In a recent paper published in Nanotechnology, researchers from China and the US reported a new type of silicon carbide nanowires – periodically twinned SiC nanowires, which have a contoured surface on the nanoscale. The nanowires – with a hexagonal cross section, a diameter of 50–300 nm and a length of tens to hundreds of micrometers – feature a zigzag arrangement of periodically twinned segments with a uniform thickness along the entire growth length. Computer simulation demonstrates that the zigzag columnar structure is formed by the stacking of hexagonal discs of {111} planes of SiC. The authors proposed a minimum surface energy and strain energy argument to explain the formation of periodic twins in the SiC nanowires.

The twinning structure has made the nanowires exhibit different luminescence and chemical stability. In another paper published in Nanotechnology (2006, 17 2870), the Chinese group showed that the silicon carbide naowires with beaded morphology can greatly enhance the tensile strength of an epoxy composite. Therefore, the new type of twinned SiC nanowires is expected to find important applications in nano-composites.