Macroscopic yarns

Researchers at NASA’s Langley Research Center, the US Department of Energy’s Thomas Jefferson National Accelerator Facility and the National Institute of Aerospace created a new technique to synthesise the boron-nitride nanotubes (BNNTs). They are highly crystalline and have a small diameter. They also structurally contain few walls and are very long.

‘Before, labs could make really good nanotubes that were short, or really crummy ones that were long. We’ve developed a technique that makes really good ones that are really long,’ said Mike Smith, a staff scientist at NASA’s Langley Research Center.

The synthesis technique, called the pressurised vapour/condenser (PVC) method, was developed with Jefferson Lab’s Free-Electron Laser and later perfected using a commercial welding laser. In this technique, the laser beam strikes a target inside a chamber filled with nitrogen gas. The beam vaporises the target, forming a plume of boron gas.

A condenser, a cooled metal wire, is inserted into the boron plume. The condenser cools the boron vapour as it passes by, causing liquid boron droplets to form. These droplets combine with the nitrogen to self-assemble into BNNTs.