May 25, 2006
Carbon nanotubes collapse with powerful force to extrude and squeeze metal wire
Carbon nanotubes collapse with powerful force when bombarded by electrons and have potential as nanoscale extruders, cylinders, and jigs Engineers use a variety of tools to manipulate and process metals. For example, handy "jigs" control the motion of tools, and extruders push or draw materials through molds to create long objects of a fixed diameter. The newly reported findings suggest that nanotubes could perform similar functions at the scale of atoms and molecules, the researchers say. In the experiments, nanotubes withstood pressures as high as 40 gigapascals, just an order of magnitude below the roughly 350 gigapascals of pressure at the center of the Earth. The researchers filled carbon nanotubes with nanowires made from two extremely hard materials: iron and iron carbide. When irradiated with an electron beam, the collapsing nanotubes squeezed the materials through the hollow core along the tube axis, as in an extrusion process. In one test, the diameter of iron carbide wire decreased from 9 nanometers to 2 nanometers as it moved through the tube, only to be pinched off when the nanotube finally collapsed. This picture shows an iron carbide wire thinning as it moves through the nanotube as the wire collapses.