KCl crystallization within the space between carbon nanotube walls

The arc discharge method has been used hitherto to encapsulate metal-containing structures within carbon nanotubes 1, 2, the arrangement of the nanotube walls playing an important role in the process. We show that KCl can be generated in the space between nanotube walls by treating potassium-intercalated uncapped tubes with CCl4. A relationship between the KCl crystal domain and the hexagonal carbon network is thought to give rise to preferential formation of a 100 plane perpendicular to the tube axes.