Strings of spherical carbon clusters grown in a catalytic arc discharge

Strings of near-spherical, multiwalled carbon clusters grow in a carbon arc discharge when nickel or iron is present. They consist of ten to twenty 'beads' of 10-20 nm diameter, nearly equal in the same string. They touch and deform each other in the contact areas, carrying a nickel or iron particle of approximately the bead diameter at one end. Termination by a catalyst particle is common to catalytically grown carbon nanofibers. However, the phenomenon reported here lacks continuity of fiber growth at the metal-graphitic interface, and requires a different explanation for the interrupted, repetitive sequence of near-spherical cluster growth.